Solo'd the raid boss tonight; wasn't too tough once I found a 'special' spot to snipe from. Wasn't able to get a kill screen because I forgot F12 is the hotkey and he slips under the ground pretty fast once he dies. I was also surprised when he died since he still had about 10% HP left. Guess he dies when he runs out of tentacles.
I used to solo Crawmerax with Roland. There was a little ledge at the edge of the cliff you could stand on and duck so he couldnt see you. Then I'd just toss a turret when it was up, and while he was distracted with the turret I'd keep hitting him with my Leviathan. I'd only get hit by his minions if at all.
Does your spot work like that, or is it still a tough fight?