Yeah, if you're a warrior Wynne is probably very helpful, her healing is essential (I got the healing spells on my Arcane warrior up enough so that I could leave her out and be relatively safe). I'd suggest putting in a tank (assuming your warrior isn't set up as one), plus Morrigan and Wynne. But I liked the two mage set up (hell, I liked 3 mages), and someone else could probably tell you an equally helpful strategy.