Here's some unsolicited feedback. Long, so applogies in advance. This reflects my opinion only and no more information than people on this list have:
1. Re-taking the GMAT doesn't make sense to me if you're already in the median range. Even if one gets an 800, it just shows that the applicant can do almost any grade school math problems in 2 minutes....this is just a hurdle to pass to show that you can grasp basic concepts and shows you can get into study mode if needed.
2. Taking the stats waiver might be beneficial but I wouldn't put too much weight on it. Given that they ask almost every admitted student to do the waiver suggests that almost everyone that gets admission, does so without taking the waiver exam.
3. Re-writting essays are useful if you feel you weren't able to do your story justice and didn't get enough time to write properly. Psychologically, I think it helps because they are forced to read your story again and remind themselves why they liked and put you on WL to begin with. On the other hand, if you're not substantially improving your essays, or if you contradict your first submission, it might just piss them off.
4. Any change to your position or resume that would better describe your role and responsibilities would help in my opinion. Doesn't have to be a promotion only. Could be a new project, a different cross functional group you're working with, a salary increase based on your annual review (showing you're a valued employee and have potential)
5. It's frustrating to wait, but try to keep in mind that the adcom likes your application to put you on WL - they don't have time to waste reviewing your application again in comparison with new applicants, if they didn't think you had a really good chance. The WL is just giving R3 and R4 applicants a fair chance, albeit at the cost of frustrating you.
Hope this helps in some way
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