A Pure Mage is viable. Magic Missile is the mage's primary spell. It does leave the caster somewhat vulnerable to tough attackers in melee range, but that's what jumping and rolling are for - to stay out of melee range. And if you're worried about tough attackers in melee, the mage has a spell for that too - Firewall.
As for Attributes, a mage needs to really worry about Intelligence more than anything else. Spirit is not that important, because you get 7 more mana each time you level up, you can reduce the cost with Mana Efficiency, and Intelligence increases your mana regeneration rate.
Intelligence also increases Magic Damage, so your spells will be more powerful as well.
Spirit and Vitality are useful, of course, but don't over-invest. A pool of 800 mana doesn't really matter if your mana regenerates so fast that you effectively only ever deplete 200 of it at once. My mage didn't really bother much with either of those and turned out fine.
Don't get Strength and Dexterity up to more than 15 or 20, and even that might not be needed.
