Why is bond of stone even a keystone?

Lets be honest with ourselves here, I know that the damage masteries are getting nerfed down to 3%... but, how is 4% which is a keystone, worth basically the same amount as a tier 4 mastery?

Honestly, you guys are looking at the damage creep, but you forget that you have tanks slowly dying because of overloaded kits, so instead of nerfing their damage, you go straight for the tank nerfs.

First it was gold gen, and passive lanes. Then it was in combat healing, rip fon. Then we decided to remove in lane base health regen. Then we removed basically all mana regen. Then we even removed supports abilities to heal, except soraka (who was nerfed) Then we had The bork, sated devour meta. Don't forget, non-tanks were too strong with 20% cdr on spirit visage, so that was nerfed. Then Randuins was too strong, so we messed with that. Somewhere in the middle of the last 4 we started adding true damage and knockups to everything, while limiting tenacity options. Then we took a step further and nerfed tank items for being abused by adcs (sterkes gauge and graves ect... ) Then we started to nerf tanks base stats in their reworks (Sion, Morde, and ect...) Now we have the armor pen meta...

I'm pretty sure I missed a few things including things like dodge removal, buffs to %hp, lifesteal increases making tmail useless, mercurial scimitar building out of qss. Oh yea, and the best damage reduction in the game is on an ad item... #balanced