At least all the accidents that happened when I was there recently were due to the what I mentioned. I did feel a lot safer about the midairs, the school purchased a bunch of Stratus's and foreflight for everyone, so every flight and traffic on their iPad, Luke SATR makes a huge difference. At the end of the day, yes training foreign students in the busy Phoenix airspace is without a doubt more risky than most other instructing jobs, but thats just the nature of the job.
The school has gotten better about rushing students through solo due to those crashes, management came out and said if you don't feel comfortable don't sign them off period. However on the flip side they do push the students into the solo stage. Once again, it comes down to the instructor, one of my coworkers had a student who has pretty bad and they instructor refused to sign him off, management trusted him, put the student through a flight review, the student didn't meet standards and was sent home. From my time there, the instructors who got into problems were the ones who put logging flight time ahead of teaching their students properly.