People need to understand that thorn mail is actually good vs lifestealers for one good reason:
If you are a tank and have a lot of resists (armor in this case) the adc will be doing very little dmg with each shot. This means they will be lifesteal ing a lot less. This is because lifesteal is calculated based off of the amount of damage dealt and not a flat amount. Auto attackers that heal on hit (same amount of heal no matter how much armor the enemy has) like aatrox (his w) , xin xhao ( his w) ,ww ( passive and q) and irelia (her w) are actually quite strong vs thorn mail, because they will out sustain it.
Now a yi, tryndamere, jinx, Tristana, twitch these all get rekt by thornmail, because they heal for so little from purchased lifesteal, that will be eventually wore down to very low hp if they decide to focus down the heavy armor with thornmail person. (They would have to buy a lot more than 15-20 % lifesteal that they usually buy to out sustain the thornmail,)
HOWEVER, ever since the introduction of the new last whisper items, black cleaver becoming popular on adcs and maw and mercurial being in almost very adc build, thornmail has never felt weaker.
A buff is most definitely needed:
I would either:
- change the damage returned from magic to true to ignore the overwhelming amounts of mr bought on adcs
2)change the formula from
15% of dmg dealt plus 25% of armor as bonus magic damage
To 15% (+5% for every 100 armor) of dmg dealt is returned ( still magic dmg)
Also the last whisper items are a slight issue because they render half your bonus armor null and void which is not ok in my opinion.
Black cleaver needs to stay away from adcs because it actually reduces armor which in turn reduces the thormails effectiveness(since you have less armor)