On the DP discussion in Firelands (nhc at least) there are occasions on nearly every boss where it's safe to use. Shannox when stacks just reset, Beth when you come down for the devastation, ryolith when stacks from volcanoes are low and no spark is about to spawn, alysrazor while the birdie is eating a worm (even though no need for it on that fight), baleroc during fireblade or right after decimation, domo during transitions or before the first leap and on rag during transitions aswell.