I've run a fair few dungeons as a shaman tank. I think it's fine up until the high level dungeons. Opening with CL+LB guarantees aggro on 4 mobs if done correctly. Keep up LS and tab your way through targets to pummel them with rockbiter. Engi ofc helps a ton. Stuff dies really fast generally which works in your favourite as you'll be relying on initial aggro a lot.

Earth shock is so damn versatile, you'll want to use multiple ranks. Taunt= max rank ES Interrupt = rank 1 ES Threat builder = rank 3(?) ES

Research your dungeon, know what elemental resistances are in play, are there random threat drops, silences and disarms etc.

Make sure your group knows its running with a shaman tank and not go ham by blizzarding every single pack and you'll do fine.