Where the hell did you get this from? If anything, all mages are much, much stronger than before. Compare a 40k CL before BB to a 150k CL after BB.
Post BB, I/L's can freeze, stun, and slow. They are great at debilitating their enemies while doing decent damage. They have fairly decent DPM in 4th job now, as before BB all mages were at the bottom of the damage list.
Moreover, Thunder Spear in 3rd job is super sexy and you'll have lots of fun.