Yeah, you should have NO problem with trash pulls. In fact, I never ever have to heal during a trash pull (only top off afterwards).

I use:
- 5 Wrath
- 1 mana spring, 4 healing stream
- 4 grounding, 1 wrath of air
- 1 stoneskin, 4 stoneclaw

With that totem rotation, make sure the stoneskin/stoneclaws drop last. Right when you drop them, fire your first salvo of lightning bolts at the mob that hurts you the most (Usually I target those priests, because they AOE). They should die before they get to you. Then, target the next toughest melee, and lightning bolt them. Most people want to PEW PEW CHAIN LIGHTNING... but you really should not do this until the 4th or 5th spell cast (basically, wait till the mobs whack the stoneclaws and get stunned, THEN chain lightning). If there are too many melee, make sure you have all 5 shammies with a key that drops fire nova totem. That saves my ass from time to time.

For the Nexus Terror's (those voidwalker looking guys that fear). Make sure you DPS them hard and fast, and theyll never get the fear off. I usually do, LB, LB, CL, LB, shocks, dead.

For healing, check out the 5x Shaman PVE Wiki page that I helped make. There are excellent ideas for healing on bosses.

On the general topic of mana tombs... I leveled there from 66-68. I then went to Netherstorm to do quests, and realized that a ton of them are collection quests (/wrists). Last night I flew back to Allerian Stronghold and put my hearth there. I'm gonna start to try Sethekk Halls.