So on certain fights where your earth eles are all dying too quickly. I move my lightning bolt from position one and replace it with a macro like

this will heal the target of the boss (if you have the boss focused)

/cast [target=focustarget] Lesser Healing Wave

odds are you will run out of mana fast on your main but this should buy you enough time to get the job done.

As for the first boss in heroic Mana Tombs there must be something you aren't doing right. Usually I just nuke the crap out of him and he is either dead or at ~5% by the time he phase shifts.

As for hints on Quag I drop all the earth eles by the water and pull out my healing macro then nuke the crap out of him also. Also try to swap out a grounding totem for a nature resist totem and you should be golden. When i was learning slave pens I had more problems with the crab packs than any boss.

One thing that I might be overlooking is that I am using orcs so I might be getting a little more dps at the start from my racial. Give it time/practice and you should be able to do most heroics. Sometimes Earth eles don't pick up bosses very fast and that makes it a wipe. In that case just go do something else for 20 mins then come back and try it again.