I'll echo what the others say about the Holy Paladin. Glyph for Holy Wrath so that it can stun the elementals, plus HoJ can stun them (I can guarantee both of these work, I do have an hpally alt that has cleared Rag).
When I heal this fight as Disc, I help as much I can with damage via Holy Fire & Smite (I don't even think I have my Mind Spike and Mind Blast on my bars =X) and usually do around ~70k damage per transition. I throw in a Penance if I feel the elemental is moving rather speedily and close to the hammer. So having your Disc Priest and other healers do some some damage can help (I know Holy Paladins can't really do much in terms of damage, but their stunning utility is great. I can't speak for Resto Shamans as I am unfamiliar with them).
For Shadow, I just Mind Spike + Mind Blast burst (and I might throw in a Mind Flay to slow the elemental a little or if he's almost at the 50% mark).
Make sure everyone prioritizes getting the adds to sub 50%, NOT prioritizing killing them (unless they're going to hit the hammer). Choose to single target nuke over AoE.