Great thread! OP put a lot of work/thought into this.
Most content I've bought here (or elsewhere) has been pretty poor. A couple have been good, but on average the articles read like a special ed student slapped at a keyboard. I've always asked for adjustments in the poor cases and eventually got them. In these circumstances it helps to be nice, but insist on fixes. So as a rule you should assume the "real" TAT is double what they quote. And when you find a good content provider STICK with them.
-ThopHayt