I got as far as 20 using both blm and nin, but always running out of time before getting enough mobs to level high enough for my liking. Can only manage to get to about lvl 22-23 on 1-10, then about 32-33 11-20. Spent 15 minutes running down the clock on lvl 19, but very few mobs respawned, certainly not enough for any kind of levelling.