With the current design, what happens with sorting if cues for events such as ASOT 550 were like this:
Title: A State of Trance Episode 550.6 (2011-03-31) (Live @ Brabanthallen in Den Bosch, The Netherlands) (A State of Yellow) (Part 8)
Performer: Armin van Buuren
Title: A State of Trance Episode 550.6 (2011-03-31) (Live @ Brabanthallen in Den Bosch, The Netherlands) (A State of Yellow) (Part 8 - Bobina)
The cue would still belong in the A State of Trance category but the cue performer reflects who the DJ is for that part of the show rather than in the title, which makes more sense to me than saying the performer is Armin van Buuren.
I end up doing this with my tags in foobar so I can find sets by DJ.
even though you're technically right and we should put Bobina in the performer field since, well, he's the only DJ in that cue but due to bad old habbits, stick to using the category's DJ name, unless that category is Various or one of those categories where DJ's are too diverse. ASOT is 99% AvB so I'd stick with Armin van Buuren for the performer.