"I am being told that its like you are paying for a job which people at 300 hrs dont deserve"
Who told you that.....oh, wait, it was me....
PACE mins are 250 total. A guy just got hired at XJT with 650 total and 350 multi from ATP. Years of instructing? Who told you that?
To be fair, that guy did an RJ transition course. Might have saved him six months of instructing. Whether it's worth it is in the eyes of the beholder.
Instructing is a great way to build confidence and mature as a pilot. It's good "seasoning". At the same time, you do it for a while and you move on. That's the way it is. Your "years of instructing" to get qualified for the regionals is probably more like six months to a year. Heck, Mesa's mins are 1000/100 without any special programs. MAPD/PACE is just another way for JO to make a buck.
To answer your question, though, I don't believe Mesa pilots are looked down upon, in general. You'll hear some pretty strong rhetoric at this site but I don't see it playing out in real life. I helped a buddy of mine who was a Mesa checkairman get on a UPS a couple of years ago. Not sure what the deal was but he got a class date right away while many guys were swimming in the pool.
I don't like MAPD/PACE cause it puts super low time guys in the right seat of an RJ, where they don't belong. Beyond that, working for Mesa won't hurt you with your next job. Working for JO isn't pretty, though.