Counter Attack

Counter Attack is defensive skill available to players 400 and above.
Unlike other skills, putting the maximum skill points on this one is not necessarily good.
Here's the official description :

Uses 0.25% extra stamina (per point) to add 0.25% to both attack and damage. (Both values are rounded up, vs. creature only)

Without doubler, that simply means 2 stamina per round of attack. That means this buff is completely useless without a doubler. Since it also means it uses extra stamina, this buff is useless if you are already 1-hitting without the buff. It is only useful when the extra attack/damage allow you to 1-hit, when without the buff you would be 2-hitting. However, selecting the level of the buff you will want can be tricky.

3x doubler
With 3x doubler, up to a level 133 CA, 1 extra stam is used, making each round of attack using 4 stam instead of 3. With a level 165 Wither, you have almost a 1/3 chance of 1 hitting, so that makes it an average of 5 stam per attack (2 attacks will use 6 stam, while 1 attack will use 3 stam). This means this buff is still very useful if it can convert the 2-hit into a 1-hit. But the extra 33.25% attack/damage must allow you to 1-hit. Since the level 165 Wither is 5 stam per attack average, that makes level 134 or higher CA quite useless.

Level 1-133 CA : 4 stam / round of attack (Level 133 = 33.25% extra attack/damage)
Level 134-175 CA : 5 stam / round of attack (Level 175 = 43.75% extra attack/damage)

Compare ::
Level 165 Wither : 5.01 stam average / creature
Level 350 Wither : 3.9 stam average / creature

4x doubler
With 4x doubler, up to a level 100 CA, 1 extra stam is used. 5 stam per attack, compared to a level 165 Wither which will use 6.68 stam on average. Even using the level 350 Wither potion is still inferior because that averages 5.2 stam per creature. Above 100 CA, 2 extra stam means 6 stam per attack, still better than a level 165 Wither.

Level 1-100 CA : 5 stam / round of attack (Level 100 = 25% extra attack/damage)
Level 101-175 CA : 6 stam / round of attack (Level 175 = 43.75% extra attack/damage)

Compare ::
Level 165 Wither : 6.68 stam average / creature
Level 350 Wither : 5.2 stam average / creature

7x doubler
7x doubler comes from the Super Doubler Potion. These potions were dropped by creatures found in Scavenging (I cannot remember the name of the creature). These potions can be traded.

Level 1-57 CA : 8 stam / round of attack (Level 57 = 14.25% extra attack/damage)
Level 58-114 CA : 9 stam / round of attack (Level 114 = 28.50% extra attack/damage)
Level 115-171 CA : 10 stam / round of attack (Level 171 = 42.75% extra attack/damage)
Level 172-175 CA : 11 stam / round of attack (Level 175 = 43.75% extra attack/damage)

Compare ::
Level 165 Wither : 11.69 stam average / creature
Level 350 Wither : 9.1 stam average / creature

10x doubler
10x doubler comes from the Potion of Supreme Doubling. These potions are sold in the Auction House under 'Special'. These potions once bought are bounded and cannot be traded or given away. Now, this gets tricky, as you will want to determine how much extra attack/damage you will need to 1-hit.

Level 1-40 CA : 11 stam / round of attack (Level 40 = 10% extra attack/damage)
Level 41-80 CA : 12 stam / round of attack (Level 80 = 20% extra attack/damage)
Level 81-120 CA : 13 stam / round of attack (Level 120 = 30% extra attack/damage)
Level 121-160 CA : 14 stam / round of attack (Level 160 = 40% extra attack/damage)
Level 161-175 CA : 15 stam / round of attack (Level 175 = 43.75% extra attack/damage)

Compare ::
Level 165 Wither : 16.7 stam average / creature
Level 350 Wither : 13 stam average / creature

11x doubler
11x doubler comes from the Potion of Acceleration. This is a potion you can make from a recipe. Many level 400 players opt to get level 36 counter attack, making this setup probably the most useful, especially if that 9% extra attack/damage allow you to 1-hit. Also, note that since you will be 1-hitting, you can consider the suicidal setup and forgo defence and armor, but do remember, you can still miss (2%) or creature can dodge, and you can die. But the 1-hitting vs 2-hitting pay off is so great that usually it is worth the risk, especially if you can find some place to stash the gold as you hunt.

Level 1-36 CA : 12 stam / round of attack (Level 36 = 9% extra attack/damage)
Level 37-72 CA : 13 stam / round of attack (Level 72 = 18% extra attack/damage)
Level 73-109 CA : 14 stam / round of attack (Level 109 = 27.25% extra attack/damage)
Level 110-145 CA : 15 stam / round of attack (Level 145 = 36.25% extra attack/damage)
Level 146-175 CA : 16 stam / round of attack (Level 175 = 43.75% extra attack/damage)

Compare ::
Level 165 Wither : 18.37 stam average / creature
Level 350 Wither : 14.3 stam average / creature

16x doubler
16x doubler comes from the Potion of Greater Doubler. This is a potion comes from scavenging, and it used to be 11x. HCS made a recent change and it is now 16x.

Level 1-25 CA : 17 stam / round of attack (Level 25 = 6.25% extra attack/damage)
Level 26-50 CA : 18 stam / round of attack (Level 50 = 12.5% extra attack/damage)
Level 51-75 CA : 19 stam / round of attack (Level 75 = 18.75% extra attack/damage)
Level 76-100 CA : 20 stam / round of attack (Level 100 = 25% extra attack/damage)
Level 101-125 CA : 21 stam / round of attack (Level 125 = 31.25% extra attack/damage)
Level 126-150 CA : 22 stam / round of attack (Level 150 = 37.5% extra attack/damage)
Level 151-175 CA : 23 stam / round of attack (Level 175 = 43.75% extra attack/damage)

Compare ::
Level 165 Wither : 26.72 stam average / creature
Level 350 Wither : 20.8 stam average / creature

21x doubler
HCS gave a bounded item, Christmas Present 2008. It is a level 1000 doubler with 240 mins duration.

Level 1-19 CA : 22 stam / round of attack (Level 19 = 4.75% extra attack/damage)
Level 20-38 CA : 23 stam / round of attack (Level 38 = 9.50% extra attack/damage)
Level 39-57 CA : 24 stam / round of attack (Level 57 = 14.25% extra attack/damage)
Level 58-76 CA : 25 stam / round of attack (Level 76 = 19.00% extra attack/damage)
Level 77-95 CA : 26 stam / round of attack (Level 95 = 23.75% extra attack/damage)
Level 96-114 CA : 27 stam / round of attack (Level 114 = 28.50% extra attack/damage)
Level 115-133 CA : 28 stam / round of attack (Level 133 = 33.25% extra attack/damage)
Level 134-152 CA : 29 stam / round of attack (Level 152 = 38.00% extra attack/damage)
Level 153-171 CA : 30 stam / round of attack (Level 171 = 42.75% extra attack/damage)
Level 171-175 CA : 31 stam / round of attack (Level 175 = 43.75% extra attack/damage)

Compare ::
Level 165 Wither : 35.07 stam average / creature
Level 350 Wither : 27.3 stam average / creature

Now that we have so many different doubler level, I thought we should have a table that compares them. Comparing stam is unnatural, so we have to divide that by the doubler multiplier, since the xp given is multiplied by that. That'll give us the xp per stam compared to straight 1-hit. I also added comparisons for staying back one level, for those tough levels that may require high level of CA.

Buff \ Doubler	3x	4x	7x	10x	11x	16x	21x	Bonus
CA19							1.05	4.75%
CA25						1.06		6.25%
CA36					1.09			9.00%
CA38							1.10	9.50%
CA40				1.10				10.00%
CA50						1.13		12.50%
CA57			1.14				1.14	14.25%
CA72					1.18			18.00%
CA75						1.19		18.75%
CA76							1.19	19.00%
CA80				1.20				20.00%
CA95							1.24	23.75%
CA100		1.25				1.25		25.00%
Back level (1-hit)	1.25	1.25	1.25	1.25	1.25	1.25	1.25	NA
CA109					1.27			27.25%
CA114			1.29				1.29	28.50%
CA120				1.30				30.00%
Wither 350	1.30	1.30	1.30	1.30	1.30	1.30	1.30	NA
CA125						1.31		31.25%
Back level (CA25)						1.33		NA
CA133	1.33						1.33	33.25%
CA145					1.36			36.25%
Back level (CA36)					1.36			NA
CA150						1.38		37.50%
CA152							1.38	38.00%
CA160				1.40				40.00%
Back level (CA50)						1.41		NA
CA171			1.43				1.43	42.75%
CA175	1.67	1.50	1.57	1.50	1.45	1.44	1.48	43.75%
Back level (CA72)					1.48			NA
Back level (CA75)						1.49		NA
Back level (CA100)						1.57		NA
Back level (CA109)					1.59			NA
Back level (CA125)						1.64		NA
Wither 165	1.67	1.67	1.67	1.67	1.67	1.67	1.67	NA

So what's really better? Is it better to use 11x or 16x doubler? I've been asked this question quite a lot, so perhaps I should write it down here. My typical hunt usually use about 1800 stam in hitting, and 150 stam in walking while using 11x doubler. Yours may differ. If CA is not needed, then clearly, the 16x doubler is better. I would have used only 103 stam in walking, saving 47 stam. If CA is needed, and CA25 works, then I would have used CA36 and 1964 stam hitting, while CA 25 will use only 1913 stam, saving 49 stam (in addition to the 47 stam in walking). If CA 36 is not enough, and CA 50 works, then clearly 16x doubler is better again. Now, the tricky part comes when CA 25 is not enough, but CA 36 is enough. With 11x and CA36, I'll still be using 1964 stam in attack, but with 16x and CA50, I'll be using 2025 stam in attack. So I use 61 stam more with 16x, minus the 49 stam saved in walking, I still use 12 stam more. But wait, there's one more saving grace. I would have hit fewer times with 16x, so I will use less blocks on an imp. I'll say I use 1 block less, worth 8 stam, so I am down 4 stam. Unless all my levels are as such, that 4 stam probably don't justify the cost of changing doubler potion between levels. Another intangible on the 16x doubler is the time you need for your hunt is reduce by 30%. That could mean to some, no rebuff, or fewer rebuffs.

Assist Buff

So today, I was trying out the assist buff. Players level 250 and above can gain the skill to cast this buff. It is under the Defensive skill tree and cost 30 stamina (very costly) to cast this buff. But the base duration of this buff is 120 mins, more than sufficient for most. The buff is also available as a potion, which can be bought in the Auction House. The potion will be a level 150 buff with a duration of 30 mins. A level 150 buff means it should activate 7.5% of the time, quite nice if that activation can convert a 2-hit into a 1-hit.

Here's the description

+0.05% per point chance of one of your allies assisting in combat vs. creatures. (Ally is randomly selected and adds 50% of their attack, defense, damage, armor and hp - note this also excludes allies whom are more than 25 levels above you.).

Note that ally is randomly selected and adds 50% of their stats. The description says it excludes allies whom are more than 25 levels above you. However, Laughsalot in guild chat said he had used this buff and never observed any players below 25 levels assisting. I decided to test it out on my own. I had help from UlyMe and rhann123, UlyMe is more than 25 levels below me, while rhann123 is just 1 level below me. I used the potion buff, and had rhann123 assisting me. I have not observed through my hunt any assist from UlyMe, sufficient for me to conclude that players 25 levels below are also excluded.

I also wondered what happens to the buff when I have no eligible ally. Will there be a message indicating activation, but got no assist due to lack of eligible ally? So I removed rhann123 and never got any message. So when there are no eligible allies, the buff just stays passive silently.

Now for the strategies in using this buff. It does not make sense to have an ally randomly selected. So to make full use of this buff, one should have only ONE eligible ally. That ally will have to be equipped to serve a purpose.

Offensively, that ally could have additional damage, to convert a 2-hit creature into 1-hit when it activates. Note that since this is not a separate attack, that means the damage that needs to be added is [Creature HP/2]*1.053, ignoring armor, assuming the player has just enough damage for 2-hit. But since only 50% of the damage is added, it is quite hard to get add that amount of damage. Instead, the player probably will have to have a lot more than just enough damage for 2-hit, and use assist to make up the difference. So here are the equations :
[Ally Damage] > ([Creature Armor]*1.1053 + [Creature HP]*1.053) - [Player Damage])*2
This use of the assist buff is probably the most useful, but could be hard to achieve in terms of ally damage.

Defensively, that ally could have all armor, to protect against creature piercing. This is the part that bothers me a little. Does the ally armor (50% of it) get added before the creature does its piercing, or after? What's the difference one might ask. Let's say the player and ally both have 2000 armor. If the armor was added before piercing, then the damage done will be based on (2000 + 1000)/2 = 1500 armor. If the armor was added before piercing, then the damage will be based on 2000/2 + 1000 = 2000 armor. This was the case in my test with rhann123 as my assist ally. The actual numbers were a little higher, but if it ws the latter, I should receive only 1 damage when both assist and piercing event occurs in the same combat. However, I died, showing armor was added before piercing is computed. As such, for defensive use of assist to be useful, the ally will need to have double the armor of the player, assuming the player have just enough armor to defend against a non-piercing strike. Like the damage setup, that is again unlikely, so maybe it can be used to make up the difference if the player was closer to double the needed damage. So here's the equations for armor setup to be useful :
[Ally Armor] > ([Creature Damage]*1.1053 - [Player Armor]/2)*4

Having the ally gear up for attack or defense does not seem to make sense.