I'm not sure this would help all that much... When we used to run T5 and T9 it was always with one tank anyway. The extra DPS made things easier not harder. Unless they think very carefully about the mechanics of the fights and implement something drastically different it could all become a little... boring for the remaining tank. At least tank swaps and mechanics involving the two tanks positioning etc make things interesting otherwise it can be about standing and being hit.... which although is intrinsic to the role is pretty boring.

What would worry me is the impact this would have on the area of the game we struggle on tank wise. I personally only play PLD for my FC static. In most other content outside our regular raid nights I play bard. As a bard it is rare with party finder that I have ever struggled to find two tanks, especially with the cross world functions of party finder for eight man content.

Four man roulette however is another story. We still struggle to find tanks. Tanks are the "in need" roll 99% of the time and if many people who off tank in a static are steered towards a DPS job most people will full time that job... then the problem we have with lack of tanks in four man content is compounded when square have tried to encourage so many people into tanking.