Thanks for all the replies.
We tried with 2 healers on Cho'gal , but this lead to random deaths with mind control on healers at aoe heavy times , what we did was switch to a new 3'rd healer (wasn't spectacular but ok) and the healer replaced improved his alt 's gear and he replaced the lowest dps we had last week , and after one 2% wipe and another 1% wipe(both because ppl entered phase 2 with too much corruption , so they took unhealable dmg by the end) we finaly downed cho'gal(6 'th try of the night).
Nefarian coming this week , hoping hes not that much harder then cho'gal witch pushed our dps , and even healers (in phase 2) to the limits