My basic tactics:
Sorceror. You have 6 time stops at that level (actually more, if you Cha bonus is at least +9). Stack them, one after the other. While hasted, of course.
Now, bombard with various levels of empowered Magic Missile. Assuming you average double-empowered, that's 25 (avg) damage per missile. You can do this twice per round (haste). You have six time stops, averaging 3.5 rounds each, resulting in an average of 21 rounds to act as you will. That's 42 spells you can cast, -5 because some of those are time stops. 37 magic missiles. Eleven out of twenty will penetrate SR (assuming you have spell penetration), which means you can rely on about 20.
That's 500 damage, in your first round. The dragon is down to 22 hit points (possibly more, or possibly dead).
Your 17th-level Transmuter cohort (Leadership), well, he's only got two time stops. But he only needs to do 22 damage, not 500. I think he can handle it. If not, maybe your horde of Monk followers can come up with something, even if it is just praying for natural 20s (note that you're all wearing similar costumes, and well-dispersed, so the dragon's chance of finding you is slim to begin with.)
Of course, all this is screwed if your Dragon has shield up, but you're a sorceror, you can improvise. Substitute other damaging spells for Magic Missile, you can probably pull similar damage.
Alternately, you can throw 12 finger of death spells in there. 8 should penetrate SR. Of course, his +28 Fortitude save means that you need to get up to at least DC 30... Requiring a +11 Cha bonus. Let's say you have this (that makes 14 finger of deaths you can do, 9 get through, plus an extra time stop to play with.) Assuming the dragon makes all its saves, it's still suffering in the neighborhood of 250 damage, and you have time left to bombard it with other damaging spells.
Of course it can buff against death effects, gaze attacks, magic missiles, energy forms, et cetera... That's why you need a variety of things in your arsenal. Don't know if there's any way to ward against time stop (if there is, there goes that tactic), but if there ain't, you can sure whip some damage in.
