I think the best part of this is the 'from the totem', so for me on trash I would be consecrate/~holy wrath, on the shaman magma/nova.

On boss fights where magma don't last the length of the fight or you don't want your shaman that close to the mob. You have the opportunity to drop totems, back off and remotely aoe the mobs/boss.

So then I would be dropping wrath/searing totems and then backing off and then pulling the boss to the totems. During the fight the shaman's rotation would include some sort of nova if there adds summoned from the boss or what have you.

This is sort of true of the fire elemental totem, in that the elemental won't be the emitter of the nova, but the totem will be.