Is it do-able? Yes.
What happened to me was a death run after the boss ko'd me. I got back only to be jumped by the boss, 3 loxes and a couple of deathsquitos. I couldn't do anything to really thin them out, as I did in preparation for the fight initially. The 4 or what ever percent of damage/ hit points changed by the number of players withing a certain distance just don't level out right. 2 players, twice the damage done. 3 players, thrice the damage done and so on. Not to mention the bosses attention being pulled from player to player in mp doesn't happen in sp. The little changes to make loxes tougher (and keep Yagluth from falling in pre-prepared hole's to keep him pinned) make things much tougher for sp balance. It should be stated that I love the game and have hundreds of hours in it solo, and I know it's best played cooperatively, but these "updates" are making it harder for sp's.
Out of curiosity, did anyone else run into this with Yagluth and how did you guys fight him?