IMO, what tanks need are more tanking abilities.

ATM, WARs are already in a good spot since they are gated by wrath/abandon to balance out their offense and defense.

DRKs are gated by MP. A bit more tweaking, and they're done.

PLDs need to be gated by something else. If they're supposed to be the most defensive tank among the rest, then it should reflect through their abilities. i am thinking of a resource that is only gained from blocking. And their future abilities are dependent on that.