It's really not that difficult to level up a low level PvE class.

DPS queues suck, yeah, but all you really need to do is one low level roulette and duty roulette guildhest a day. With those two combined you easily get around 2 levels each day.

And I speak from current experience in leveling Dragoon up to 34 for Blood for Blood. DPS queues suck, yeah, but it's nowhere near "impossible" to do. It just doesn't take as quick as leveling a tank or healer.