I am not sure how you are 3 healing these fights? On Siegecrafter progression, we had 2 healers and both pulled over 25m damage each (going DPS cloaks, the priest going DPS meta).
Siegecrafter took us about 130 or so wipes, Klaxxi took about 140, but that is not normal. We just had a night of wiping on Klaxxi due to not having 2 of our main raiders available which probably added about 50 unnecessary wipes.
Even on Klaxxi, on 10 man, you need the dps. Still can't fathom how people are pulling these fights off with 3 healers.