I typically just leave tank stance on all the time.

If the other tank is crummy on aggro... Well, Shirk exists for a reason. If it's really bad, then I'll toggle it off for a bit (Usually one of my burst combos is enough to create a large enough gap to not worry)

However, there's little recourse in either scenario. Leaving it on or off.

So long as you're 2nd on aggro then it doesn't matter at all. Especially since the enmity changes basically means that DPS/Healers pretty much don't have any enmity compared to like 1 burst combo with tank stance on...