Its situational to me; really depends on the tank and what mobs are around.

If I have time to Repose, and the tank is marking enemies, I'll Repose the last enemy (mine is a macro, so its noticeable that I'm doing it). Haukke Manner and Cutter's Cry are two I use it a lot in; also the poison plant mobs in Tam-Tara (hate having to esuna 3 stacks of poison)

However, if the tank isn't terribly good or there's too many mobs I won't Repose, since doing so may kill the tank (in fact, I was tanking Stone Vigil and the heal was Repose-happy...so much so that he let me die to about 6 mobs trying to sleep some [funny thing is, I think he pulled the second group...])

I don't Repose in WP or AK normally though...its just not worth it (WP speed-runs there is a use before the first boss, but since we run with a BLM its normally his job to do it.)


As for DPSing...if you have time to do it (tank is stable), go ahead. If the tank is not...you better be healing.