Thornmail should apply heal reduction
It would make more sense for a tank to have this trait (now more than ever with warlords bloodlust granting up to 20% life steal for free). Since tanks are most likely not going to be able to burst down a carry, let alone chase one down (thank you iceborn gauntlets and swifty boots and all the crit items that give movement speed), being able to mitigate their already great potential to sustain would make the most sense when on a tank. A role who is built around longer skirmishes and absorbing damage, while having a low DPS.
to name a few.
All these have great regen/shields and either high damage scaling AOEs or %health scaling abilities.
There is not a single champion in this game who can only be used as a damage sponge
I think that's it. Remember though that there are very few "pure tanks". Many of them can be more or less called "very heavy fighters" because, well, otherwise it would be boring. There is no pure black or pure white. For example, Alista, Leona and Braum are the purest tank of them all, while on the other end we have Amumu, Sejuani and Shen, with more power invested in damage, but still tanks.
into tank items





in the botlane would be the dirtiest **** in the history of League of Legends if they implemented this. Rito make it happen