Personally, I agreee about the Mages being the best class.
A high priest or Grand druid can compete, but that is about it.
Personally, I dual-class from a fighter if I can - because then, the mage at low levels has planty of hit points, correcting the largest deficit of mages.
In SoA I dual classed my fighter I brought in from winning BG & now have a L11 mage/L9 fighter - with 135 HP & a base THACO of 12. I actually planned to dual-class, but the level limits in BG were so low, after I got SoA I decided to wait. Oh, but I miss my cloak of balduran