Agree with all you wrote, Vaxsan, except the last paragraph. Even at level one you can do combos like Midnight Oil + fire staff. And of course at level 5 you can take Glass Cannon to be capable of casting more than one spell per round. If you do all the Cyseal quests you're not far away from level 5 if my memory serves me right.

The problem with combos including two characters is exactly that the two casters may not be in the right initiative order or may be too much apart for the combos to function.