I think it's probably a bad idea to let the wizard have an action. Orb'ing someone to death with direct damage is difficult to stop, but if you give the wizard a chance to act, you never know what spell combination he'll fire off, especially since he knows his divinations have failed on you and that's a clue about the level of the threat as well.

What if he decides to toy with you instead of going for the kill, and drops a Timestop > Dimension Lock > Whirlwind of Teeth > Forcecage combination on you instead? You can prepare for this situation (Rod of Cancellation,) but there's a dozen dozen nasty tricks wizards have, and if you forget even one then you'll be suffering for it. I really think the best way is to slaughter him before he gets his first action... it's the only way you're sure that you'll still be standing when your next action comes up.