I spoke to my sound engineer freind about why the sound on Sunday was such a mess. He said that the feedback that he people near the front had a more balanced sound means that they were getting most of their sound direct and not from the PA. He also agreed with the observation that drum kit, bass, keyboard, guitar and spot solos need to be miked up but the brass and saxes just need a little to capture 'ambience' but not much more.
He also thinks that the reason for the uneveness is that the sound engineer should have 'swept' the room. This involves a tone generator and playing pink noise and white noise and measuring the response around the room. This identifies dead spots, hot spots, standing waves etc which can then be compensated for and so ensure an even distirbution of sound.