Wizard, when do they turn the corner?

[Stonewallx39]

I've always heard that Wizards are back loaded as far as power. As in the first 20 levels are very difficult and a Wizard will be under powered but eventually catch up and surpass other classes.

At what point does this happen?

I've heard Wizards have a better resist modifier but a lot of spells seem to resist fairly regularly. Unless there is a unseen factor it seems other classes will always outshine Wizard in terms of utility and sustained dps.

Are wizards destined to a life of taxi service and soloing or do they start to offer some real value later down the line?