Like most people have said here... Mages are really squishy, but do a lot of damage. I mean, hell my Veno has barely 11k phy defense in normal form and I'm not complaining. And really since some classes are getting nerfed at the moment and others aren't, I'd say enjoy your class while you can, sooner or later there'll be a nerf for every class so it can be more even. But even that won't stop people from complaining about others.. :c
Soooo, learn to get used to the classes? Learn to play them? Learn how to react if you get the "fire debuff", or the "owl" or, or. Yea, always gonna be something, get used to it.
Just my sayings.