All in all I'm not a big fan of those spells. You'll have to keep investing points for the damage to scale, and you become very dependent on mana. Only magic missile is usable as a main weapon (1s cooldown), but the damage is only on par with a bow (that does not require a such heavy investment). The others are on a 15s cooldown and the damage is not even remotly close to what you get from thousand cuts or splitting arrows.
Endgame, Magic Missile is actualy far more powerful than anything you do in melee with similar point investments. Remember the way the spell scales, and how damage modifiers work.
It's harder with magic until level 15 or so, after that it actually gets easier as a mage than as a fighter because the spells are so powerful ^^;
