Clan_iraq's Guide to THORNS DAMAGE in PVP
This covers all sources of Thorns; Thorns Aura, Spirit of Barbs, Iron Golem, and Iron Maiden:
Hopefully after reading this you will understand why a charger can kill a thorns pally in 1 hit, taking maybe 100 damage in return, and laugh, but they charge that Summoner druid and kill himself in 1 hit, even though the Grizzly's not even dead yet!
The reason thorns is so impotent in PvP is that it suffers both the PvP and DR penalties TWICE, once on you, and once on the returnee.
Say you have 1000% return thorns aura. Sounds good. You and the enemy WW barb both have 50% DR, he hits you with a 2000 damage WW. This is what happens:
2000 Damage hits you
2000 is reduced by 1/6 PvP penalty = 333
333 is reduced by 1/2 DR penalty = 167
167 damage is reflected at 1000% = 1670 Damage to target
1670 is reduced by 1/10 PvP penalty = 167
167 is reduced by 1/2 DR penalty = 83
Your "1000%" return is really only returning 50% overall. Now lets say you both have -20 damage, from normal item mods.
2000 --> 333 --> 167 --> 147 --> 1470 --> 147 --> 74 --> 54
You take 147, he takes 54. Less then 50%.
*Thorns returns at 1/10, all other effects (like IM) return at 1/6
So overall, you'd need nearly 2000% return just to be returning 100% of the damage you take. Fairly unrealistic, considering you're also taking flat, unreturned elemental sources of damage.
Now, what happens if you hit a SUMMONED unit, like a Grizzly or Iron Golem?
The DR penalty is only applied once:
2000 Damage hits grizzly
2000 is reduced by no PvP penalty = 2000
333 is reduced by no DR penalty = 2000
2000 damage is reflected at 1000% = 20000 Damage to target
20000 is reduced by 1/6* PvP penalty = 3333
3333 is reduced by 1/2 DR penalty = 1667
That same WW that would have dealt 167 damage to you, deals 1667 back to him when it hits your bear.
Effectively, you are returning exactly 1000% of the damage, instead of 50% Very big difference.
So how do we use this in PvP?
Have your opponent somehow melee a summon, not yourself. For example, minion stacking will render Zeal a suicide skill. I should note that as of 1.10, Bone Walls no longer reflect damage with any form of thorns, nor can you leech off them. So you can't simply bone prison/iron maiden someone.
PS- Further calculations will show you that each 1% of Life Leech will negate 12% of return when hitting a summon; 50% Life Leech will negate 600% return
This covers all sources of Thorns; Thorns Aura, Spirit of Barbs, Iron Golem, and Iron Maiden:
Hopefully after reading this you will understand why a charger can kill a thorns pally in 1 hit, taking maybe 100 damage in return, and laugh, but they charge that Summoner druid and kill himself in 1 hit, even though the Grizzly's not even dead yet!
The reason thorns is so impotent in PvP is that it suffers both the PvP and DR penalties TWICE, once on you, and once on the returnee.
Say you have 1000% return thorns aura. Sounds good. You and the enemy WW barb both have 50% DR, he hits you with a 2000 damage WW. This is what happens:
2000 Damage hits you
2000 is reduced by 1/6 PvP penalty = 333
333 is reduced by 1/2 DR penalty = 167
167 damage is reflected at 1000% = 1670 Damage to target
1670 is reduced by 1/10 PvP penalty = 167
167 is reduced by 1/2 DR penalty = 83
Your "1000%" return is really only returning 50% overall. Now lets say you both have -20 damage, from normal item mods.
2000 --> 333 --> 167 --> 147 --> 1470 --> 147 --> 74 --> 54
You take 147, he takes 54. Less then 50%.
*Thorns returns at 1/10, all other effects (like IM) return at 1/6
So overall, you'd need nearly 2000% return just to be returning 100% of the damage you take. Fairly unrealistic, considering you're also taking flat, unreturned elemental sources of damage.
Now, what happens if you hit a SUMMONED unit, like a Grizzly or Iron Golem?
The DR penalty is only applied once:
2000 Damage hits grizzly
2000 is reduced by no PvP penalty = 2000
333 is reduced by no DR penalty = 2000
2000 damage is reflected at 1000% = 20000 Damage to target
20000 is reduced by 1/6* PvP penalty = 3333
3333 is reduced by 1/2 DR penalty = 1667
That same WW that would have dealt 167 damage to you, deals 1667 back to him when it hits your bear.
Effectively, you are returning exactly 1000% of the damage, instead of 50% Very big difference.
So how do we use this in PvP?
Have your opponent somehow melee a summon, not yourself. For example, minion stacking will render Zeal a suicide skill. I should note that as of 1.10, Bone Walls no longer reflect damage with any form of thorns, nor can you leech off them. So you can't simply bone prison/iron maiden someone.
PS- Further calculations will show you that each 1% of Life Leech will negate 12% of return when hitting a summon; 50% Life Leech will negate 600% return
, and then let the enemy wack your skeles around, ll% cant touch that 
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