In our LFR games we've recently been playing some 7-10s with two Wizards. The resulting combinations, when done well, were... impressive. Especially once a few dailies were involved.
The most memorable combo was when the other player's wizard dropped a Grasp of the Grave in the middle of the battlefield and I overlaid it with a Visions of Avarice. Once that combo was up and running, the battle was effectively over - all opponents dazed and most immobilised each round, our own party members unimpeded by the zones, able to move freely with no fear of opportunity attacks and automatically gaining combat advantage, and both wizards still free to cast standard-action spells each round, which took the form of a variety of area-effects centred on the zones, catching all or most of the ensnared enemies each round.
Even in earlier encounters without the dailies, two wizards co-operating to herd and impede opponents were able to seriously reshape the battlefield.