My example macro's, are for shaman's 1 & 2, in a 4 shaman set up.

On the comma, no totem is placed.
With a three shaman group, you want the sequence to be 3 actions long.
With two no-actions, and one Tremor drop for each sequence.
That way on each push, one Tremor is dropped, and after three pushes we have 3 Tremors.

Shaman 1... Tremor,,
Shaman 2... ,Tremor,
Shaman 3... ,,Tremor

The reason for the reset=5, is to re-sync the shaman's with each other.
Since you'll likely press this rapidly for 3 seconds or so, it doesn't interfere with placing the totems.



I'd go with a much longer reset on Elementals, but its the same principle.