The lag gets so bad it's unplayable. At level 20, I couldn't even move my cursor around to aim without over 5 seconds of lag. That basically caused a mob rush and my death. You really need to fix the lag or allow for a MUCH lower graphics setting to reduce it...
Echoing what EvilGM said, you can beat anybody with a poison mage. As long as you have over around 300 HP to counter the ice mages that freeze defense, you can WP through anything. Beat the hermit with around 1k MP, taking no damage whatsoever in that method.
Entlee...four conjurors is simple - just summon the golems as tanks against the legends. The conjurors' own damage output is quite nice as well. I've gotten to level 330 of the Endless Evil with a group of 4 conjurors, warriors, rogues, mages and barbarians. Clerics take too long, and rangers are kinda useless unless you manage to find a good spear for one of them. 3 Mages + 1 Warrior is quite nice as a setup really.
Apparently, the legendary monsters are every 15-20 levels or so?
And my way of not overcrowding my inv is to always keep a stash of 2-3 Shop Scrolls handy in case the 'ole inventory fills up.
 "Elona Shooter"){kind=icon}
 "Medieval Rampage 2"){kind=icon}
 "Book of Mages: The Dark Times"){kind=icon}
 "Monsters' Den: Book of Dread"){kind=icon}