For my end, mostly I'd want the tanks to have fundamentally different ways they generate their aggro.

That is, the x10 aggro modifier on the stances can stay, so long as it affects something different on each class. For example, Warrior should get a massive (x50 or so) boost to threat generated, but only on healing they cause, no matter on whom they do the healing. So all their self-healing is also how they do aggro, enraging the enemy with the fact that this unarmored 10 IQ doofus wearing just a loincloth won't die no matter how many planets they throw on their heads.

Meanwhile say Gunbreaker generates aggro every time they use Continuation, again no matter on what and maybe it's even a fixed amount that pulses in an AoE instead of based on the damage/effect of the specific continuation. Not sure what I'd do about Paladin and Dark Knight.

It's mostly flavor of course since over X minutes of fight it needs to be roughly the same threat total, but I'd love for the flavor and the profile of threat-generation to feel different between classes.