I main tank (mostly pld) and never drop tank stance during trash pulls. I do during boss fights to an extent.

My question is, is a healers dps higher than a tank in dps stance? If so, why do I see so many Wars in 4 Man dungeons going to deliverance during trash pulls? Are those crit fell cleaves that important for you?

The only tank I can see that would benefit from dropping tank stance is drk.