The problem is that when you think, "bring tanks to WARs level" you probably think about buffing damage and outright cloning WARs properties into DRK and PLD and that just isn't necessary at all. The reason WAR is so "well balanced" or "well designed" is because a lot of it skills are balanced to be useful as both an OT and MT, something DRK and PLD are horribly lacking. Vengeance and Raw Intuition? Stacks for your Triple Fell Cleave. Equilibrium? TP Recovery when OTing, HP when MTing. There are just very few skills in the WAR toolbox that are ever useless at any given time, regardless of what the Warrior is doing.
On the other hand PLD and DRK have a large numbers of skill that are just rendered useless the moment they decided to change from MT to OT (or vice-versa). DRK suffers from this the most. What do you use Dark Dance for when OTing? Reprisal? That's useless. When MTing you can't use Blood Weapon while Grit is on, forcing DRK's to treat Grit like Herpes. The duality skills have between OT and MT position is something that has been horribly implemented, one of the best planned out skills in their arsenal is Carve and Spit as it actually offers the sort of dual utility tanks need in this game. Why not allow DRK's to use Blood Weapon while on grit but with a different effect than when Grit is off? Why not just make Reprisal an oGCD that has its timer reduced by X seconds whenever you successfully parry? (Allowing DRK's to use it while OTing and more frequently when MTing). Why is Abyssal Drain so useless in most raids?
PLD's? It is a bit different but they need their utility buffed enormously and again skills need to be planned out to be useful while MTing AND OTing. SE clearly had this idea when they introduced skills like Clemency, Divine Veil and Cover but it's so half-assed that it needs some sort of overhaul. Why does Divine Veil require a heal to activate? It makes zero sense. Why does clemency scale of Spell Speed? Why can it be interrupted so easily since a tank ALWAYS takes damage? Why is cover so horribly situational? Give it extra benefits or reduce its cooldown. Bulwark is a joke and Tempered Will is useless most of the time (useful when needed but that’s situational). Again, like I mentioned before, PLD needs skill to have some sort of usage while both OTing and MTing, they have a DPS and a Tank stance, why can't their skills change a bit whenever they change their stances to reflect what they are actually doing? Maybe have Tempered Will work somewhat like Equilibrium and offer the PLD TP refresh when OTing and HP refresh when MTing? PLDs need their utility boosted significantly.
The point is that ultimately skills need to be designed in a way that they aid the tank in their duality (OT and MT), WAR is perfectly designed in this sense while DRK and PLD are just not. I mean, in theory balance between DRK and WAR is perfect (WAR has better OT damage and DRK has better MT damage) but in the end WAR always wins out because the rigid design of DRK just doesn't make it very flexible, same for PLD but to a lesser extent. PLD has crap DPS? Fine, but buff their utility ENORMOUSLY, make them like BRDs/MCHs, the lowest damage of all the tanks with the best utility (making them desirable) and for the love of god, fix their TP issues.
This can all be done without making everyone a WAR clone, does WAR have issues? Yes, it definitely does. Equilibrium is OP as heck (it should be a 90s cooldown at LEAST) and Path is incredibly powerful considering it reduces ALL damage DIRECTLY (unlike DRK and PLD, who decrease the STAT, making it a less efficient reduction), 10% STR/INT reduction =/= 10% less physical/magic damage. Path should, perhaps, have its efficiency halved.
TL;DR – All tanks should be balanced to take into account both their role as OT and MT, skills should reflect this duality. Currently WAR is the only tank that does this and this is the main reason why it's the king of tanks. The solution to everything isn't MOAR DPS.