Fight part one occurred last night. Did you know that 12th level PCs are ***holes? The sheer number of proning, immobilizing, slowing, and similar powers gets ridiculous. Add in a bard with psychic locking vicious mockery, giving the dragon a pretty much permanent -4 penalty to attacks, a wizard with mass resist energy negating most of the dragon's damage, and a warden who simply would not be moved, and I ended up with a pretty ineffectual dragon.
After his first set of allies died, Ghul Khota spent about 10 rounds trying to get the hell out of dodge, and after his wings tore off he managed to dive into the river . . .
. . . only to be pursued, on foot, for five minutes by the warden and barbarian (ram form and wildrunner means REALLY FAST). They couldn't attack him because the dragon swam faster than they could, but they paced him. The rest of the party wasn't fast enough to keep it as one encounter technically, so the two PCs who'd followed fell back and regrouped.
Yay, I managed to get the party to blow 75% of their dailies (*grumble mutter whine* stupid debuffing all being targeted on one enemy *grumble mutter whine*). Now when they go after the dragon next week, it should be interesting, and I might actually be able to deal damage to the party.