You only need one Totem of Wrath down for all of them.
But, if they're glyphed for ToW, you'd like each shammy to drop one, at least once every five minutes for the buff.

I have had ToW x3 (all shammies) on one key, separate from my totem stomp macro.
Just to push that periodically, for each to get the buff.
Currently, the team is basically doing pure PvE, so I have 3x ToW in the stomp macro.