Early Game Mages (EGM's for short, cause we're cool that way) are squishy. There's not much to be done about that. The steps above will help but when it comes down to it, Mages are destined to be kite fighters (hit-and-go) rather than pillars of fortitude.
Learning how to use mage spells effective helps a lot, too. Ice Storm can be a bit tricky to line-up right, but get a good bounce going and it can wreck havoc on anything in it's path (deliberately bounce it off walls, don't got for straight up attacks).
Summons help a lot. Anything that keeps the fighting Way Over There.
Mages grow to be powerful, insanely powerful. But it takes time.