The Man Eaters never gave me any problems, but i was a mage and i toxic/poison clouded their ass. In the second playthrough, it was even easier as i had the firestorm spell and good stats. I cast 3 in succession and they both died.
The one boss that did piss me off was the flamelurker, i honestly think the devs were trolling us with that boss. It would sometimes be a joke to kill and at other times it would be retarded hard. I remember the first two playthroughs i killed it as a joke and the third one i was stuck for a whole day with that fight.
To be honest, the bosses are jokes compared to the black phantoms in the game. If anyone went to the effort of platting the game, you'd have to play around with the world tendencies to get them to show up. I believe every world has one. The samurai black phantom,
Satsuki in World 4-1, dude that asshole raped me so many times i hated him so thoroughly. Worst part was he spawned at the start of the level so, as soon as you'd enter he'd be waiting to greet you with a katana up your ass. He is the games first AI spawn camper.
Even, the black phantom in world two gave me serious problems, Scirvir.