[Faceman]

I prefer to dual-class (with a fighter as primary) immediately at the beginning for the following reasons:
1.) You regain your abilities at the end of chapter I
2.) You can use the proficiencies you get at lvl 8 to obtain
grand mastery in your weapon of choice and ++ in your favourite weapon style.
3.) Because of 1.) you'll play the game as a straight char with very nice fighting abilities for your class.

I recommend to always dual, if you want to play a mage, because that allows you to wear ElvenChain and Helmets (no casting restrictions)