Thanks for the overview, makes this process more straight forward. You are right that the GMAT will hurt you, but unfortunately I don't see your work experience or extra curricular activities being all that much more impressive than average to compensate. GS is good, but its not IB, and also the issue you have is your undergrad school / GPA combination and GMAT are both not impressive, which would cause worry for the top business school programs unfortunately.
I would say the top tier schools are definitely a reach for you, albeit this depends on other things about you that may be different from someone else. Assuming you are relatively standard otherwise, H and S will be very very difficult for you to get into.
I would look at these schools:
NYU
UCLA
Tepper
Darden
Let me know if you have any questions, and sorry if the answer wasn't what you were looking for, but I would rather give bad news than falsely lead someone to apply to a school they don't have a great chance of getting into.
-Scott
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