So I went and tested this over the weekend - King Dred in heroic DTK.

Staggering the totems at 1 second per drop yielded an instant fear-break. The the fear icons would pop up over toons heads and they'd sorta move a little but would jsut resume casting (or just standing there as the case may be).

Dropping 1 or 4 all at once was drastically less fear coverage and I had toons running all over.