Flamelurker is the hardest boss to kill one on one. If you can't do it, I'd recommend that you just skip over and do 3-1, 3-2, and 3-3. The stages are easy. In 3-1 the black leather armor set is some very good light armor. Not the best but probably the best you'll have for awhile.
Here are some tips on the stages for the third area.
-When you fight the Cthulu enemies, roll past their spells, then let them run up to you and ring the bell and then roll away so you don't get hit by the attack. Then either melee them two handed or use magic if you're a spellcaster.
-Use your shield on 3-2. The enemies where you can fall off the edge really aren't difficult.
-Use turpentine on your weapon or fire magic to make quick work of the 3-2 boss.
-Pray that you don't get a human player for the 3-3 boss if you're not very good.
Didn't think of this until now. On the 3-3 boss. Just sign out of PSN. A black phantom can't join your game if you're not online.