I didn't even realize there was an xp boost for leveling a class lower than another. That's good to know.

Ideally I'd like to have two jobs on one character for flexibility when getting a party together. One DPS job and one high demand job like a tank or healer. I just wasn't sure if that was feasible. I also forgot about Hunting Logs as a source of XP.

About dungeons, is there a limit to how many you can do them per day like many MMOs? Or does that only apply to leves? I've only done the three story ones on the way to 20 once because getting a healer was a chore.