If that's not allowed, get Blood in the Water (Stance), Improved Critical (on any 18-20 weapon), EWP (the same weapon), a Kaorti Resin weapon (for a x4 Critical Modifier) and other stuff that boost crits, and then get a +1 Merciful Bodyfeeder weapon.
Net result = you make critical hits fairly often, hit like 4 trucks at once when you do, and half of that you get as Temporary HP. On a Frenzied Berserker, that can be a triple digit number, at least.
Why Merciful? So you don't kill your allies, and so you can beat the hell out of them for THP, if you need it badly (just use that 3rd level Cleric Spell from BoED to heal all Nonlethal damage back... Get a wand or something.) .