I honestly think this is the biggest weakness of not having specs and using stances instead. Specs you'll need to turn off/on before content, whereas as stances allow for stance dancing mid-combat.

In WoW, for example, you could level up as a Shadow Priest in solo play, and then swap to Holy/Desc for healing in late game.

If we had something similar, a WHM could spec for ClericStance for open world content, but then respec for Healing in grouped content. Their DPS would be abysmal in the healing spec, and it would be useless; however, when in open world they could respec for DPS.