It seems like for dread spikes, The Giant AOE from the summoning of good king moggle either is too much or negates dread spikes altogether.
Situations where Dread spikes is a no brainer to use is when you are about to go off your surge timer but don't have enough tp to renew it. If its going to be blown might as well use dread spikes anyways, unless you are saving it in anticipation for a big attack or something.