Your heals are all over the place. If your paladins is EF blanketing there should be no issue with a paladins healing this fight pulling 70-80k HPS at ilvl 475. If they aren't blanketing with EF, then even then 60k+ with your priest the two of you should be fine. At 35k heals your Shaman would probably be better off dps'ing if he's going to do that little HPS overall. Your bottom four dps are low (53k or below - I understand two of them are probably tanks, but they should be able to go DPS on this fight if you are three-healing).
Once we popped from 2 heals to 3, we started pushing 10 percent instead of 60 percent. And then once our DPS got better at trading the pheramones, calling out stacks, not standing in puddles during transfers and the frontal cone damage, then we were good. Towards the end one melee dps should be able to keep the legs in check while all others pummel the boss.
Setup a kiting order of 4 people, setup a cooldown rotation for the crushes, collect your loot.