e.g EA as a hatred generator instantly makes all the other generators obsolete. The only way it makes sense is to have it on a bow which doesn't do as much damage as other end game bows to force players into a decision.
Tasker making sentries shoot 100% faster is potentially in same boat.
same as stacking cooldown reduction to spam RoV.
I don't disagree with these concepts, but if an item has these cool properties then they better make it so that the player is missing out on something by equipping these items. e.g. The current SoJ is cool but equipping one potentially means you lose the cc/CD of a good rare, hellfire rings bonus. This is actually good balance.
I guess I am worried about enchant being able to make (for example) an SoJ exactly the same as a good rare but with the elite dmg bonus. Then everyone will be using a SoJ.
Blizz should be careful about making certain legendaries too powerful and build diversity will actually suffer as a result.