I guess, the main problem with this challenge ist, there are to many exploits and to many broken skills at the moment to be a real challenge.
I think it's a good way to find out what the exploits are so we can bring them to Larian's attention. The game was designed to be played with a full party, so doing the One Man Army challenge kind of forces you to find out what's exploitable.
Although, my main purpose behind this challenge was to illustrate that the game's
not too difficult as some people have been complaining. If I can beat it with just one character, then the problem is not the difficulty of the game.