Radical thought: Make Tank stance and DPS stance so vastly inferior to each other that a main tank and off tank have to choose them. Current DPS spread between tank stance and non tank stance is fine but DPS stance needs a +25% vulnerability up or so to keep main tanks from using it. Another way to go about it would be to make tank stance stronger and gear defenses lower but its fairly cumbersome. Less reliance on auto attack fluff damage, more boss casting bar attacks. Mini tank busters between stronger busters since every class has active cooldowns (innerbeast, TBN, Sheltron). Overall just give tanks a necessity to use it.

Part of the problem is how fast gear overpowers you to content, gotta love these giant ilvl gaps of 5 and 10 instead of 2 and 4... But if a DPS stance were to sacrifice mitigation for DPS instead of just adding DPS baseline, we would see alot less use of it in MT slots. +25% damage to a tank is pretty rough.

Dark knight needs a DPS stance and SE should have realized this by now. Darkside needs a DPS stance rework and grit/darkside should be less costly to activate than what grit currently is.

Well that's my two cents on this anyway.