Having played all three roles (dps/healer through all ex/coil, tank through all ex), I’d say that generally the healer has the most responsibilities. Healers have to dodge everything dps have to while still keeping everyone alive, and they need to know the fight as well as tanks do in order to plan accordingly for big hits like death sentence. And if you’re really good, you’re stance dancing and dps’ing as much as possible on top of that.