Just taken Nociduas down - I'd tried earlier and couldn't make any headway, but this time at around level 38 it was fairly painless.
I noticed one interesting factoid during the course of the fight which I didn't see mentioned above. At one point, with shades and summons attacking him, Nociduas had strayed outside his circle for some reason, so I tried an arrow to see if his shield had disappeared.
It hadn't; I got the usual message, and he seemed to be able to keep summoning too. But the arrow was from the Bow of Decay, and while he took no damage from the hit, he DID take damage from the acid on following rounds.
Don't know whether the same goes for Acid Spray, but it's possible. He didn't seem to have a huge number of hit points, so a couple of direct damage-dealers might shorten this fight quite a bit.