Two, let me put it this way, how exactly are you going to beat a bunch of Pit Fiends, a Green Dragon (Suldunessalar), Irenicus or even a bunch or Iron Golems? Being alone without a party is one of the most unwise things you can do! Besides, how boring would the game bee with Minsc's battle cries?!!
Sure you gain all the experience for yourself, but so? A meduim level party of 6 is much more powerful than a single ultra powerful main character.
Compare the fight with Sarevok and then compare the fight with Irenicus. I beleive Sarevok was alot harder because he had a quite strong party. Irenicus may have been a level 30 mage, but he fell down alot quicker than Sarevok.
