Doing The Black Loch took me six hours. My gnome illusionist is not so good with undead, though at leas TBL zombie wizards can be Phantasmal Killer'ed and there are some bugbears and kobolds.

For me the key was disarming that one disarm-able trap (I used Iessin who can search then disarm the trap). With the trap out of the way Dimension Door is a viable option again. There was a whole lot of cast DD, run around corner, Meteor Swarm and Shadowbalde then run through the DD. Tthe last part of the dungeon takes like two minutes to run from the entrance so a bit tedious.

There were more Reapers than usual including I think three high level Reapers. This time I consistently made a Vengeance Reaper dance so maybe their Wills aren't as high as I thought.

With the running back I noticed you can shoot bad guys on the boat from the ledges that overlook the boat (the ledges near the entrance to the optional chest). That save some time running back, though I couldn't hit the last boss from there. Still the boat is the easy part as you can hang back and shoot from cover as the bad guys (other than Reapers) don't come out of the boat.