The major problem was the complete lack of an emergency plan by PHX airport/BA, i.e. why was everybody left on the tarmac for about 20 mins?
The staff are however exceptionally good at collecting excess baggage fees for return travel after the lowering of the recent weight restictions(even selling you a handy tote bag for $25 to put all your excess gear in and carry on as cabin baggage (two pieces, no weight restriction)), and then selecting you for a special security check thus ensuring the delight of an additional half hour with PHX TSA. The idea of 300 odd pax milling around on the apron with large aircraft taxying around and no plan does not surprise me (have been using PHX for the past 12 years on a regular basis).