Random minor tidbit I remembered for some reason or another when we BST trio'ed a Black Abyssite: Kenesu was using Crude Raphie on Yilbegan, and Raph appeared to be immune to the doom from Soul Douse. The possible reasons for this:
1. Crude Raphie is immune to Doom
2. Crude Raphie resisted the Doom but not the HP-down, and having the HP-Down applied prevented the Doom of subsequent douses from taking effect. It sure seemed to last a long time though.
Because Yilb seemed to mostly use Soul Douse when being tanked from the front by Raphie, it became a much easier fight. Could be something for later reference or other Zilant dragons that the HP-Down will prevent Doom if that's found to be true.