Spell casting in D&D is very complicated. The management of a wizards spell book is a key skill a PNP player needs. They only have so many spells they can cast each day and if they pick the wrong spells they're useless.

First they need to decide how to balance their spell book between protection spells, enhancement, healing, attacking, and task-preforming. Then each spicific spell has certain components needed. (eye of neut, gems, etc.) Then, in a tatical situation, the speed of casting a spell plays an important factor. This is a lot for a casual play to do, and if they get it wrong, their gameplay experance suffers.

After all that they finaly cast their spell, only to find out their target made a "saving throw" and the spell didn't work anyway.(It's no wonder few people played NWN as a pure spell caster).

On the development side, making sure each of the hundreds of spells does what the rules say is not easy.

In Dragon Age the spell caster still has a wide range of choices for spells, but instead of managing a spell book, they'll be managing power. They can cast lower level spells more often, but still have to reserve some power for a big monster.

The exact nature of spells in Dragon Age is still being balanced, so I cannot go into anything more spicific.​