Even if DPS queue takes 40 minutes, that still gets you through your Roulette queue and dungeon in about an hour, and at these levels you're pretty much guaranteed a full level just from that alone even if you don't do anything else with that class. Add in some FATEs while you're waiting and you can make it more like a level and a half. Be sure to alternate between different regions for the FATE grinding, though. There are a couple FATE challenges for doing a variety of them, so it's less effective if you stay in one area repeating the same ones.