If the MDR thing is fixable by option tweaking, then I'd say go for it.I agree that the MDR issue is unacceptable. I find that I can fix it in v20 by disabling "Damage Fix" from ToBEx core, and "Concentration not broken on zero damage" [or whatever it's actually called] from ToBEx tweaks. So at the moment I'm leaning towards distributing v20 and making those deactivations in the install code - but noting that people who want to run v21 are welcome to. Thoughts welcomed, though.
Another thing bit me in SCS II v19 (and may thus be worth testing with a new TobEx) was the lack of backstab immunity for barbarians. (The preview fixes this too, JFYI. It may have been fixed in TobEx 20.)