and, one feature of the archmage prestige class is counterspelling mastery that allows him to not only counterspell something cast at him, but also turn the spell back on its caster. So, a targeted dispel magic would not only be countered, but would (in turn) be cast upon the PC, potentially dispelling several of the PCs buffing spells.
There is just one problem - counterspelling itself is generally quite sub-par and deemed a serious waste of a good standard action. You are wasting an action not doing anything, and you getting to act hinges on the PC spellcaster doing something. If he catches on, he can simply opt to do nothing, while the rest of his party closes in.
IMO, it really only becomes worth it at lv27, when your caster can access the epic counterspell feat (which lets you counterspell an unlimited number of times each round as free actions).
Also note that spell power was revised to now give +1 caster lv instead of improving your spell DCs.
The PCs have the advantage with their 4-5 actions to the wizard's one each round, so you need to even the odds (typically by attempting to spam as many spells as you can). Make sure you are able to manage 1 quickened spell each round, and you can never have enough timestops to cast those crucial spells (this is where archmage's SLA power comes in handy).
Consider judicious use of sculpted spells (fairly undercosted for its benefit, IMO) so you can consistently catch at least 4 PCs in the AoE of whatever you are throwing at them.
I also don't see why you can't simply timestop, then dump multiple forcecages on key PCs (it is not a targetted spell, so you can use it to contain dangerous PCs even in a timestop). Only maze is subject to such a limitation. Whether you should, however, is another matter altogether...
Some conventional defenses include greater mirror image + displacement (quickened if need be), stoneskin (sucks, but it helps ward against silver weapons).
You may also want to prepare at least 1 celerity as a last-minute middle finger to the PCs (ie: when you could die, celerity - timestop - spam as many spells as you can before teleporting away).
You also don't really have that much hp (average 130hp for a cr22). Might want to find a means of boosting that somehow (eg: improved toughness, various sources of temp hp, desecrate aura).
You could also consider procuring that diamond mind maneuver which lets you substitute a fort save with a concentration check (if only to hedge against disintegrate).
Yep, playing a high lv wizard is like some sort of chess game. You need to identify the potential threats and nip them in the bud before they can even take root.
