I don't really agree - a good dj's bad set should still be worlds away from a bad dj's bad set.

I've played in a club before that had no monitor, and a massive main room, and although it was my worst set, i've heard worse by people who have had everything set up ok. The structure and placement of a mix and track selection is in my eyes what matters most, and a beat slipped out here and there because of bad equipment is excusable when you hear a good dj mix (and they should be able to rescue it pretty quick anyhow).

A badly placed mix or a poor track coming in is mainly what would make me think that someone is a bad dj, and that doesn't really have anything to do with the club's set up or decks, more the person's ability.