I agree with most of your points, but I do have some info.I CAN confirm that shiny Pokemon can spawn (I've gotten a few) They're just rare (with the exception of the guaranteed shinies).
Also, I have not experienced the problem with prey escaping your Pokemon so easily and frequently. Maybe it has something to do with gaps in levels? I don't know. Maybe the Pokemon you're using just has a hard time keeping stuff down.
Gotta agree with that shed in the pred safari being too small though. Although the encounter frequency is pretty normal for a Pokemon game. If you don't want to be interrupted there's always repels.