@Meddler: Is there anything going on with Thornmail?

Even in its edge cases, Thornmail has poor effectiveness by this point. It's basically got the same problems as WotA did, only worse.

Enemies counter it by getting magic resistance or lifesteal, or by dealing damage with abilities rather than auto-attacks. This greatly defeats its purpose and effectiveness. There are also new items that hard-counter Thornmail: Phantom Dancer, which reduces incoming Thorns damage by 12%, and Death's Dance, which staggers 15% of the Thornmail damage over time, both which make Thornmail highly ineffective.

Players who use Thornmail need bonus armor for the actual damage, HP so they don't die, and MPen so the magic damage of Thornmail isn't reduced by MR. Unfortunately, most Thornmail users can't also get MPen without gimping themselves as tanks or fighters, leaving it easy to counter with magic resist.

I have run several games where I got Thornmail and in all cases it fail miserably. Whether I was Rammus or Malphite or rushed it against a team with 4 AA-heavy Champions, it simply floundered in what it was meant to do: punish auto-attackers. In virtually all cases, they would take pretty much no damage from it.

Unfortunately, to my understanding, buffing the item is not permitted due to it making the edge Rammus/Malphite cases too strong. This probably indicates that the item is in a toxic state, much like WotA was (only Vladimir got it, and it dictated his balance). And as such, it feels like it would be better to either rework or remove the item rather than simply try to rebalance it.

Worst of all, no one at Riot ever wants to discuss the item. It's as though you consider it a taboo to do so. But I have to ask: what's going on? What is planned for Thornmail, if anything?