Part of the issue is that separation in amount of damage that can be done between different PRE is multiplicitive when in destinies, rather than additive.
The question still stands: How much should a tank have to sacrifice in DPS in order to focus on tanking and defense. With the way destinies are set up right now, that separation is huge. On my barbarian, I can completely destroy epic elite mobs when in either LD or FotW, but on my paladin, if I fight one mob, I feel like its going to go 12 rounds, and I might win by decision if the refs think I landed more blows than the opponent did.
So, when melee offense builds do this much more DPS than melee defense builds, the issue is that if the melee defense build cant hold aggro, all that defense the player built for is worthless - as its not taking pressure off the melee offense builds. Heaven forbid tanks actually get an offensive buff, so the answer is: a buff of 1 kazillion percentage to threat generated, and hyperbole aside, pure offense melee still pull aggro from time to time.
Another part of the issue with EDs is: How many times to we have to learn the instakill lesson? The easy button EE farming ritual has become, roll with maxed wisdom monk splashed divines. A party of ED monks (or high wis builds) is as effective as a party of PMs were when the max level is 20, due to ONE ability. Everyone else has to work for it. When they first nerfed it I would have preferred a critter limit rather than a cooldown increase.
Moral of the story: Additive power creep is better than multiplicitive power creep. It doesnt get out of control nearly as quickly, and if something is more powerful additively, the stuff that is less powerful can still hold its own and is still fun to play. In a multiplicitive power creep scenario, its too easy for different mechanics coded in different eras of the game to combine to become OP to the point of hilarity and leave everything else behind.