I would have thought the way to go would be to find a single moment in his routine or his daily life where he isn't ready to teleport away if he is unexpectedly attacked, (Say, whilst buying his magical groceries, bat guano etc), and then ubercharge him.

If necessary, make sure he isn't aware you are present, then uber-charge from hiding.

Of course, if he does have nerve-skitter or so on then you're pretty much out of luck, and miss chances aren't going to help. Likewise if he's currently immune to HP damage, which I've heard is possible.

Perhaps it would help to have an uber-charging leadership posse, as It'd only really take one good hit to do him in.

Fully defence-focused optimised wizards will pretty much not be going down to anything short of Diplomancy, because quite frankly if they are doing it right, even the tier 2 caster stumbles because such a Wizard should have 20-celestial-questions divined till he knew of all such threats and had chance to prepare in advance.