I would agree with Denti that the company actions as you have described them are excessive for what is a small exceedance.
Not sure if you have things like 'unions' to assist where you are, but I would look anyway at:
1) The Company Ops Manual/perceived company procedure for descending from high level ie VNAV to be used as primary tool?
2) If so, what guidance/warnings/training you are given on its use
As Denti says, 20/20 hindsight now will have you both using LVL CHG in future, and Denti's Fleet Manager is talking horse **** and would appear to have little practical experience of the a/c! 'Protections' in VNAV are virtually non-existent and what 'protections' there are are only effective when the old horse has bolted and not before.