Let me predict how the tank balance will be in 5.0.
New tank: deals 2x the damage of a dps, has a permanent 50% damage reduction... just permanent and that is before all the 20s lasting 10s cooldown def buffs, buffs the entire party with 20% damage up and mitigation by simply looking at the boss.
PLD: Will have a shield, just a shield since a sword = to much damage and you might trip and fall on it.
DRK: Will have a mp pool of 1 without any way to increase it, also the sword is a tupperwear sword since it would be dangerous otherwise.
WAR: Has an axe... well not as much an axe as a stick with the word axe written on it, also get a new skill at lvl78 by the name of "poke it" that makes the war poke themselves in the eyes so the screen goes black while the war and the player of said war see nothing, "poke it" share keybind with all the other skills.

But seriously, should PLD be nerfed? No they should not. What should happen is that SE actually listen to the tanking community and balance the tanks. There are countless suggestions on the forums, heck there was countless people voicing their concerns after the media tour after which SE did nothing to change things, had SE listened then we might not have this horrible mess... a mess that will not be solved by nerfing the one tank that happens to be in a good place. There are many things with the current state of tanks that I am angry about but all but one of those has to do with what a needless mess they made out of war, the only other thing is how SE fucked up our attack power calculation.