Yes, I too spent 90 minutes killing the phase spiders with Lae'zel's mage hand alone, just to see if it was possible. But it took 90 minutes. I only really find cheese objectionable when it both makes the game easier and saves time. If there's a big enough time to cheese tradeoff a player has to make a choice to make the game more boring in order to make it easier.
If you really want OP, Mirkon with the Minotaur greatclub is OP. If anyone was keeping track of such things, I could easily have a world record speedrun, murderhoboing every NPC in the game with him.
But once they fix the Glut above ground glitch, I'll have to manually throw his body to Underdark in order to raise him from the dead. Quite tedious, and a difficult task without taking care of the phase spiders first.