Opinion: Tanks should be balanced around Rod of ages/ Liandry's/ Sterak's....
If riot intends the tanks to deal some damage
I personally believe that Tanks should be easier to balance if they incorporate one and ONLY ONE damage item into the tank builds, namely s5 Maokai/Nautilus/Gragas, pre rework zac, pre nerf Sion etc...
This stops riot having to gut items such as Sunfire, nerfing hp + tweaking base damage(fucking up the damages) which caused triple dorans start.
Catalyst should be the mana item that tanks rush to survive lane.