Turns out there were a couple more rooms that I wasn't aware of. I also found some sub-zone issues where standing in the corner of a room caused the wrong map to be displayed. The following image and XML fix both problems (thoroughly tested this time). Only one of the two images needed an update.
Code:
<ImageStyle Name="exp18_dun_vacrul_raid_01_0" displayname="Castle Vacrul: Thirst for Power [Raid] (Reverie)" zonerect="-343, -76, 60, 271" availablerect="-343, -76, -43, 271">
<ImageFrame Source="images/maps/map_exp18_dun_vacrul_01.dds" SourceRect="0,0,597,512" />
</ImageStyle>
<ImageStyle Name="exp18_dun_vacrul_raid_01_1" displayname="Castle Vacrul: Thirst for Power [Raid] (Reverie)" zonerect="-343, -76, 60, 271" availablerect="-43, -76, 52, 70">
<ImageFrame Source="images/maps/map_exp18_dun_vacrul_01.dds" SourceRect="0,0,597,512" />
</ImageStyle>
<ImageStyle Name="exp18_dun_vacrul_raid_01_2" displayname="Castle Vacrul: Thirst for Power [Raid] (Caverns)" zonerect="-46, -243, 373, 353" availablerect="-43, -243, 373, 353">
<ImageFrame Source="images/maps/map_exp18_dun_vacrul_02.dds" SourceRect="0,0,512,729" />
</ImageStyle>