10 for both. Shamans should be priority over any other type of add. The wave after the first 2x Drake wave will have a miniboss and a shaman in it, don't even think about touching the miniboss until the shaman is dead. Have your DPS make target macros for the totems, they have 50k HP and should die before a tick goes off. They can be a little difficult to see when everything is clumped up so have everyone yell out in vent/mumble when they see one drop. As far as interrupting the chain heal, have the ground tank save his interrupt for it, while others can worry about interrupting the tidal wave. Letting heals go off is the fastest way to ensure you'll get over run.