Whilst I generally love Dragon Age, it has some major AI issues, and I'm pretty sure I ruined it by playing through as a mage first time through, for most of the game my party consisted of 3 mages and Alistair and it got faintly repetitive, it took me one spell from each mage to kill every White enemy on screen without being hurt, then a single further spell to kill any remaining yellows, Orange enemies were harder but not much due to aforementioned awful, Awful AI (basically you can make melee enemies chase one character whilst it runs around in circles, whilst the other members of your party sit and shoot from a distance).
In summary, Fun game, Overpowered Magic, poor AI.
Also whilst trying to avoid spoilers, do female characters get a version of Morrigan's deal at the end?