Difficult

[n00bLar]

I don't find mage hard to lvl. In fact I think they lvl pretty fast. You just need to know how to use your spells and how to kite :-)

It's true that mage lacks def and hp but the damage that your spells make makes up for that more or less :-P

[Loveless]

First time I actually played a mage is this game and it was so easy... I got to Lv17 in a matter of hours (yay for KQs).

With the magic... you should use
Lightning -> Ice -> MM -> Fire ->MM Rinse and repeat.

If you can't kill the monster with just one cycle of this then get your butt out of there. :P