with my 4 shaman team, I ran without a tank (and rare heals) from 30-60, exclusively in dungeons.

Scarlet Monastery to ZF to BRD, to LUBRS to outland where I switched over to questing.

During that time, I geared for pure dps. The cool thing about BRD and LUBRS is that the groups tend to be 3-5 at a time. Punch out the first 1-2 mobs before they get to you, and the chain lightning has probably spread the agro on the rest around. Whichever of your guys crits will get agro for each mob. Anyhow, I just committed to dps and killing them before they killed me and it worked all the way to 60. Try to keep up with good shields along the way, that's the only piece of gear I concentrated on.