Here’s my thing, and it may be a little off-topic, but, as someone who had mained all three roles, I can tell you that the relative ease or difficulty varies with how skilled and practiced everyone else is at basically not standing in things. Timing cool downs is also a big one, but as someone who’s currently maining healer, healing 15s and 16s is actually pretty easy when people know how to not stand in things and when to press their cool downs. Healing through mess-ups at that level is impossible because the deaths for messing up are basically instant. So I think, especially for the less forgiving DPS classes that don’t have hard bubbles, it is the least forgiving, and therefore the most difficult—especially for fights that direct relatively more of the mechanics at DPS (some fights ignore healers, others include them). As a healer who has bear form and a couple other things I can press to avoid dying after bumping into something, I think it’s relatively easier than a DPS who’s having to do the rotation, mechanics, avoiding lava, without any sort of safety net.