I agree, the Phoenix show would have been cancelled/postponed due to ticket sales if that was truly the reason. The arena out in Glendale is a long drive for casual fans so their choice of venues contributed to a non-sold out performance. The show was absolutely phenomenal despite the empty seats! The issues in Dallas were non-existent here so really, I understand their need to postpone some shows. Seriously, if you can reschedule around work or whatever, do so.
Local reviews for that show:
http://www.phoenixnewtimes.com/music/5-incredible-things-we-saw-at-the-muse-concert-7878249
http://www.azcentral.com/story/entertainment/music/2015/12/06/muse-concert-review-drones-tour-glendale/76883136/
I got lucky when explaining to my employer my plans for San Diego were thwarted, and he agreed to give me the January days off instead! I am so ecstatic about the Arizona show, Ill see them in San Diego and will most likely continue on to Vegas!
Ugh, I've become a Muse drone...