basically put points only into brutality and/or tactics for most of the run then while you're in the castle — or just before you reach the castle — grab a few survival scrolls so you get +70%, +60%, and +50% (not exact numbers) bonus to your 3-4k hp. you can really get a lot of hp just before hotk by doing the above and resetting your mutations and picking dead inside for another +50%. i've definitely walked into a hotk fight with ~11k hp and didn't have much trouble beating it even with underpowered weapons