Vorbis is totally fine for this - very few people can ABX FLAC and ... gosh, I don't even remember the Vorbis equivalent of V0, but I think -q5? (assuming you're using q5!). It would be exceedingly unlikely to a) have someone who (theoretically) can ABX them and b) someone with the audio equipment to ABX them combined with c) someone who plays ADOM and d) someone who just won't stand for lossy audio.
P.S. IMO, (as much as most Hydrogen Audio people have their head screwed on right) LossyWAV really has no niche. FLAC is great for archival purposes (and what I have most of my classical music in), but realistically most people can't ABX FLAC and V0 MP3 (and MP3 is a pretty shitty codec!), much less have the audio equipment for it. Anyone who does shouldn't be worried about the space that FLAC takes up. There's definitely no point in using it for ADOM.
gate closers: GeWi GnMo(unarmed) DeAs/Pa/Mi(staves)/Ra GePr DrBb HrMo | p7: MeBf | p17: GnPr | p20: DrDu GnAs DeCk MeWp OrBf GnTh MeHe | R57: MeDu | R101: DrAs (26,674 turns) GnDu (26,748) DrAs (18,533)
ULE: HeRa OCG: DeMi
currently speedrunning DrAs.