Yeah, I think blocking the doors with the rod is our best bet. gives us some time to get ready. After that... I don't know, but ehre's some ideas:
-Move Oceas into Melee. He's got as much max HP as Deigh (which ties for highest HP in the party), and Deigh's hurt. Give Oceas as much AC boosting power as possible and try to get hom to soak some.
-Deigh has two bottle of Tholos Blood he's been saving for just this occasion. Each one makes a weapon Flaming (Tormaling?) for 5 rounds. Deigh will use one, I would say Luvaine or gelvin (or Oceas, if he tanks for us) gets the other. Deigh also has two bottles of Antitoxin, if we need them.
-If we're trying to get a jump on Nockmort, and we have some time to prepare, Deigh could loan his dagger to someone else. This dagger gives +2 to initiative, so it may be useful if, say, we have a spell that we REALLY want to cast before he can do anything.
-Assuming roughly equal reach, Deigh can move up to Nockmort, hit him, and move back out beyond where Nockmort can hit him each round. (20 ft in to within 10 ft, attack, Spring Attack back to 20 feet out, and we know these guys move slow, so we hope he moves less then 20 feet in a single move).
-Deigh also has a Masterwork cold Iron mace, if anybody needs a weapon.
Deigh's current HP is 32 out of a max of 50. He has no other status ailments, and no abilities that recharge/have uses per day.
So, overall, I think our best bet is to figure out an alternate 'win' condition. What are we really trying to do here?
If we do go toe-to-toe, I say we block the door, summon an elemental, have Oceas tank for as long as possible, let Deigh spring attack each round with a Flaming Chain, and generally try to not get killed. I'm also all in favor of removing the rock, at worst it does nothing, at best it weakens him or returns hi to sanity.