I've been leveling my alt classes through the DF exclusively, and doing a couple of Leves if im really close to a level at which i get a new dungeon.

If you're leveling a new class to 50, find a friend interested in doing the same as a Tank or Healer and get faster queues. Or level a Tank yourself.

Hunt around for FATEs while doing the Hunt Log. Do a Crafting or Gathering class while in the queue if you don't have friends.

Or just suck it up and cry in a corner until your DPS queue pops. Your choice.