Thornmail is a "must have" item on rammus, it's been nerfed to the ground; I'd like you to kick around the idea to have thornmail return all damage and/or return the form of damage back as the same type of damage, i.e., return true damage for true damage. There are many champs that auto attack, but not basic attack such as silver bolts which never proc thornmail.
Try this idea out on PBE, see what it's like.
Thornmail is a "must have" item on rammus, it's been nerfed to the ground
It actually hasn't changed that much.
Vs. 167 total AD or less on Thonrmail's bonus armor it's the same vs. raw AA power, vs. 333 AD or less it's the same vs. 200 bonus armor.
Considering Rammus can get 130 bonus armor through Defensive Curl with Thornmail alone that ain't bad.
Those AD values may seem a little low: but consider early and mid game phases are really important, and a full-build 6 item build is pretty rare. Average per-game income is 11k per player, or around 3 major 3k items, 1k in boots, and 1k in the bank when someone's Nexus explodes, for a ~33 minute long game. With 80 essentially being the max AD a single 3k item can get (barring Occult, it's only use being "that guy" in a co-op Vs. AI game), and ~110 being a pretty standard level 18 average for AD, you're looking at a max of ~340 total AD in a typical game.
Granted - worse vs. Critical Strikes and Spellblade procs, but it's better against a wide range of on-hit effects, so no more Jax, Kog'Maw, Teemo, or Kayle slicing through your armor-heavy build like butter. Pretty neutral change overall considering the number of on-hit effects in the game.
Concerning "nerffed to the ground" for Rammus in particular: with that 120+10% armor steroid, I'd say it's more an improvement and buff as far as Rammus is concerned. His build pushes him to want armor and build armor even in face of mixed damage due to how well he scales with it, and the Thornmail change makes him much more relevant vs. such on-hit champions than before, where he's still plenty useful vs. everyone he already was strong against.
I'd like you to kick around the idea to have thornmail return all damage and/or return the form of damage back as the same type of damage, i.e., return true damage for true damage. There are many champs that auto attack, but not basic attack such as silver bolts which never proc thornmail.
The main issue I see with such a change to thornmail is this:
Most on-hit effects seem to be intentionally designed to be less effected by armor than alternative routes. Maybe it's because you're a tanky DPS champ reliant on crushing that 1 defensive item a squishy builds so you don't get out-tanked by them while also being out-manuvered and out-ranged. Maybe it's because you're a high-risk, high-reward champion set up to dance around people in Rune Prison perma-CC range.
This change would generally cause the opposite to happen: Relatively low-risk physical AAs would deal less damage just through merrits of armor being roughly 50% higher than MR on everyone through bases and itemization, loosing out a Last Whisper in free penetrations: while inversely making the thorns much more devistating and hard-hitting vs. champions with play-styles much more susceptible to being shut down with heavy defense, and thus given defense-piercing mechanics to even out the risk/reward factor.
It's also worth noting most such mechanics don't benefit from life steal or spell vamp at all, which is essentially the main purpose of Thornmail: to prevent life-steal.
If Thornmail was about AFK killing people, giving you the power to slay an opponent by just standing their, preventing them from countering it in any way outside of avoiding you entirely - it wouldn't be in the game.
