Good god, have you even played this game at all? Wizards cannot do big damage to single figures consistently, their shtick is basically to kill weenies (aka Minions) in the early rounds of combat. I'm currently playing in three separate campaigns, each with a wizard, and the thing that is most obvious is that the wizard has a very narrow, specific role in the game. No way in heck is he "the best" class, he's got his role like any other.
Honestly, just seeing you type those words makes me 99% sure you have not even played the game and are just dancing around with contextless calculations.
You're missing the fact that the wizard's powers tend to have nothing which consistently just wallops individual characters. The majority of his combat powers are weak area attacks with interesting rider-effects while his non-combat ones are interesting reality-warping effects.
A wizard cannot Evasive Strike to shift out of the way of several attackers and then pound one for 2[W]+stat, force every enemy on the board to get pulled next to him only to wallap each one for a full attack AND mark them until the next turn (Come and Get It), can't heal anyone (the first reason your suggested all-wizard party will be turned to paste in the first few encounters) and simply can't fight toe-to-toe with a "boss" character of any kind for any amount of time.
Seriously, get a few games under your belt and come back here, I guarantee you'll have a different opinion.