There probably 5 different ways to play. Just pick one that matches your play style. I use defense and no tank. 5 shammies. 3 have increased stoneclaw. 5 have increased fire totem. 2 have melee talents (for strength and stoneskin). 5 have resto down to range on totems. Yeah, only lvl 34. I plop down 3 stoneclaw, strength, stoneskin, 1 mana, 4 healing, 4 grounding and grace of air (when I get it). I have alts lightning bolt 1 mob, 2-3 come (talking elites not normals). 2 stay on stoneclaws long enough for me to kill 1. Even if they slip off early, they go through my fire totems which buys me time (and they are cheap---talents). Now I focus on 1 of the rest and heal when necessary. I usually only have to heal about every 2nd-3rd pull. The healing totems do a lot. And if things get hard, I use 1H and shield. I have had 000 problems yet in any instance up to SM. I lightning bolt to pull and on the way to me and melee and shock when they are close.

I don't like targeting to do actions, so I focus my main and use:
/cast [target=focus-target] DPSSpell for damage
/cast [target=focus-target-target] HealSpell for heals

Doesn't matter who has aggro, I just use the same healing spell and it heals them.