It seems to me that if your character build is highly mixed, you better have some high-class manual skills to back it up. However, if you simply go with the flow and be a true warrior-class with warrior skills, mage-class with mage skills, the battles will feel alot smoother...
But I often find that boring! lol. Right now, I'm doing something that is mainly a warrior but with a hint of an archer. I like how I poison my enemies before I bash their skulls! So sneaky and clever.
What about you guys?