Also, you can't play mage as you play melee character. And even in low levels they can be "monsters" in killing most enemies with one hit. Of course, you need to use magic to achieve this (I start with fireball).
Later people say they get much stronger, but from my perspective, mage with Grissenda is pretty formidable from start. You can get Grissenda with L2-3, so, from very start mage is strong.
Mage class using Mage Armor maxed and summoner maxed I think is the strongest character in the game. But mana management is most important factor for success. Summoning a level 18 iron golem while enemies bounce off you makes you nearly indestructible. Add agility based Hirge with mystic bone and shield of wisdom and you have strongest combo with fastest way to level up. I don't even waste skill points on recovery with the mage/cleric combo. Fire spell is good early on fighting undead and trolls. Lighting good for the Ark, but spells aren't really needed. Max arcanist with wand(more fun because you can use all gear), max summoner, and max mage armor. Character is at 40% XP bonus before scrolls.