you are living by the rules of the airline that hired you. If you do not like the rules, then or now, QUIT! Your company defined when your date of hire was. On the same side of the argument, ALPA has a definition for seniority circumstances such as we have now that defines what your date of hire is. For both MEsaba and Pinnacle you can see your DOH listed right on your badge-that cannot change. You were not cheated on your date of hire because you agreed to those "terms" when you accepted employment.
I was cheated out of a month of seniority and still have 3-4 guys who I would be senior to if it were not for an HR mistake at the time of my employment. Was it my fault? NO. Am I mad about it? yes. Is there anything that can be done about it? probably not, at the time I was just happy to get a job. SO I live with it. Maybe I should be a baby and cry about the dumb HR chic who admitted she forgot to call me for a week to offer me a position. She even told me that when she called. Flight ops had to email her to remind her to call me.
If you want your date of hire to reflect the day you started class for this integration-you should have came to MEsaba-or better yet-quit and get hired here again. You will have your class date as your DOH.

stop complaining-it is in blochs hands