I think whatever Obsidian does with mages will work out well. They are not strangers to the genre, and I am sure they will do a good job of balancing the usefullness of each class.
I think it may be wise to look at P:E as a chance to do something new with some of the classes, instead of using the same old formula. That being said I am a fan of the D&D class system (even with all its problems) and wouldn't be sad if P:E's class system worked very similar to D&D's.