Just get better gear, OP. There's only so much skill will do for you. I mean, I am all for pushing the limits and do think things are skill-based rather than gear-based, but I just lodestoned you and you have a ilvl 55 weapon with your MND at a grand total of 500. For you to heal efficiently with this gear, the pulls will need to be swift and the tanks need to be on their game with the cooldowns.

You can also get into the habit of Holying - this not only boosts the speed at which stuff dies but will help you with the damage mitigation as your Holies will stun NPCs thrice in a row before they become stun immune.

Get a better weapon first and foremost, this will be the gamechanger.