That's how it is on 360 as well. I don't mind it myself.
It is a pretty huge change if you are accustomed to real time combat. Also the behavior is inconsistent. Assign a two-hand weapon or bow to the d-pad and then assign 2 spells to the triggers. This allows you to toggle weapons and magic. However if you map a shield, staff or one-hand sword this does not work, you always get unarmed. This makes no sense at all. Would you want your mage to fight unarmed instead of casting spells?