I think I know how to fix champions abusing some items..
.. Like:
+
+ 
#Negative stats.
All tank items should have some (light) debuffs on those who wear it. Damage (Ad/AP), attack speed, movement speed. And of course tanks & bruisers should be compensated for this change.
I bet most, if not all will disagree with me, but then what would you do?
Nerf a champion? Which might lead him into weak state for months if not years? Nerf an item? Which in turn ends being useless for the group it was made for?
With this, ADCs would have to sacrifice some of their stats to be tankish. Unless of course we want "glass cannons" to be tankier than Rammus.