Originally Posted by Slash7
thornmail should be taken late game
early game isnt that usefull
i think you would need mgc pen for better results
in order to counter thornmail adc needs lifesteal and mgc resist
like malmortius and king, bloodthirster
thorn helps late game but not really early game
and i think that the armor it provides would be enough as only armor item
as tank basically prefer to take firecape early cause gives hp and armor
then some mgc resist and then thornmail if needed
i remember i build thornmail on tank yi after frozen mallet
it helped me big time against adcs
No, it's the opposite. Late game auto-attackers tend to actually have the armor penetration, life steal, and magic resistance to deal with thornmail. Last Whisper, The Bloodthirster, and some level of Magic Resistance from things like auras, mercury treads, or guardian angel will generally nullfiy the returned damage. Thornmail is an item for winning duels, which is something you tend to stop doing when team-fights are a thing. It helps tremendously in duels against auto-attackers, and helps to prevent them from reaching late-game builds.
If you pick it up in the lanning phase you're pretty much invulnerable against any Attack Damage Carry, whether they're melee or ranged. Which is generally pretty effective top-lane against the 4 melee carries, as they're reliant on farm (being carries), but you're free to push them out of lane without much to worry about in terms of retaliation. Armor also helps you tower-dive, so fun stuff there. Not to mention you reflect those critically striking Parrrleys and every hit from Blade Waltz back to Gangplank and Fiora with it.
Whenever I play Fiora in Dominion that's how it works though - if I'm stuck bottom lane and my opponent rushes a Thornmail I'm more or less forced to switch with someone top lane. If the enemy squish decides to rush a Thornmail I can't kill them before they reach a safe spot or allies. If someone picks up Thornmail in the final stages of the game when I'm at full build (for Dominion, which is like 2 big items, boots, and a random assortment of components) then it doesn't help them much - and I can proceed to win 1v2s at that point.
Thornmail was removed from the faster-paced Twisted Treelines, and I'm guessing it's largely because of how much of the game is based on early fights with less items (and unlike Dominion you can't really avoid anyone in Twisted Treelines, what with only 3 players on each team). Most of the ranged attack damage carries were unplayable in there if anyone picked up a thornmail.