i've been using it constantly when swapping between jobs and it always seem to put the right gear in place... probably helps that there's gear levels and job restrictions on gear.
as for those dungeons i'm guessing they're part of the MSQ roulette so they pretty much hand you tons of currency for gearing so they'll always be lucrative for people to join. even if it's a lowbie dungeon i've rarerly encountered anyone getting snippy over someone watching the cinematics.