Belranga is easy period but yeah.
That build looks really really broken but fun. WOTW not as spammable BPM (9 wounds) but if imagined pain procs that much could still be spammed a lot in battles with many enemies (like belranga). Getting that flail is a little out of the way but probably doable. Seems like this would work best on a shattered pillar though since WOTW doesn't proc wounds (besides the imagined pain). I haven't tried a shattered pillar, maybe the threshold is too low.
Well HOW was indeed pretty easy with the Ajamuut's Stalking Cloak. I did remove the WOTW nerf though. Would be quite a bit harder requiring 9 wounds since the massive black oozes start merging on hurt and the lower ones immediately. But possibly doable. Also trashed my armor but that doesn't really matter. Don't heal fast enough to do this whole fight naked I don't think.
Would be very easy with transcendent though. Ring of Finality's Claim + Summon Duplicates and HOW does a lot of self-damage. Could actually do it from stealth but would take a while. Then when health gets low, bam, disintegrate.
But...I think transcendent has more trouble with Dorudugan than SC monk with HOW. Besides soul annihilation the cipher spells are mostly useless vs Dorudugan since he has high defenses and 50 resolve, so it is very hard to keep up borrowed defenses or psychovampiric shield.
This game with BPM in general is much easier with tanky builds just punching things...because the "unbalanced" things like wall of draining and blood sacrifice were nerfed to hell, and fighters/barbarians massively buffed. Monk was slightly nerfed in certain abilities (WOTW, dichotomous soul cost more wounds) but also transcendent suffering reworked (or might be like this in vanilla, not sure) so at PL9 FF has +32 accuracy and +180% damage, and at PL10 it is like +37 / +195% damage, with penetration 16.8, 18.8 with tenacious, 20.8 with tenacious and crusted swordfish. And you can get PL10 pretty easily, just need two of nature's godlike, crusted swordfish, or power surge from stone of power. FF in particular seems way better than other monks since FF attack gets +50% damage from curse and +55% damage from monk power level, oh, and it heals you while generating wounds. But blood sacrifice was apparently unbalanced enough to need a 6 second -100% healing debuff and 3 second recovery... FF attack is just so so much better than mythic weapons, there is no weapon that even comes close to that outside of some weird interactions like scordeo + flail you mentioned, and hardly anything is immune to crushing
---edit
just read all that about getting PL20 (or higher with bellower), sounds nuts. I couldn't get it over 10 but I didn't try a lot of those things. Imagine you'd need strand of favor to keep it that high though.