Dont forget you can shape the battlefield to your own desires as well. Dig big trenches that they can fall in but not climb out of, fill with acid.

Also, don't be afraid to push out your epic spells. Using the seeds and some careful math, you can make spells that literally do anything. Make it rain down meteors in a two mile radius all day? No problem. Emit an aura that heals you and any nearby allies for several hundred points a round all day? Easy peasy.

Find out what kind of prep-time the wizard will get before he has to face those hordes of constructs, and you can even keep the spellcast times long if you want to.