Do I have a case? No. A hostile work environment exists when there is a pervasive atmosphere of discrimination do to sex, race, etc. What you describe is an unpleasant work environment, not a HWE.
I was given my yearly review, none of the items reviewed where does not meet expectations, however my final grade was given as a does not meet. That doesn't make much sense however your manager may exercise his complete discretion upon judging your performance.
I was given a sheet of paper with my name on it and 2 peers that had items i was to complete for a performance improvement plan. this same sheet was photocopied and given to peers. My peers approached me and said "hey you dont meet expecations either" I feel this is an unbelivable breach of right to privacy. There is no right to privacy in the workplace, with the exception of certain medical information your employer may have.
-I turned in my performance impovement plan, but got no feedback from it and no one said anything about it again. Unfortunate but not illegal.
One of my bosses continusoly said "the new vp dosnt care if you or my two peers" are still with the company anymore. This was said lowdly and in publid. Extremely rude but legal.
one of my other bosses would consistatnly berate me and other employees in front of those we wer supervising, undermining my ability to execute my performance improvement plan. Again, very rude but legal.
-I was not paid shift differential when i was assigned 3rd shift because i was a "manager." however no one would ever answer when i asked about it. There was no policy about this in the proicly and procedure guide when i left the company. Employers are not obligated to give anyone a shift differential. If they don't want to pay a shift differential to managers, they don't have to.
There have been complaints about the one boss who berated me, HR "investigated" but did nothing about it. If the complaints were basically about the boss being a jerk, they aren't required to do anything about it because being a jerk isn't illegal. Additionally, HR doesn't have the authority to "do" anything about the boss, even if they want to. All they can do is advise senior management of the fact that he's a jerk and recommend they do something about it.
If you were terminated because the new VP wanted to bring in her own team, that's legal too. All you can do is file for unemployment benefits and start looking for a new job. Good luck.