Sorry to hear of your plight InChina.
I would agree with the comment's about VNAV's tendency to dive for the path regardless of speed and the dangers of hitting VNAV and assuming all will be well. I've seen the 'clacker dive' in the sim and on the line. We're taught to use LVL CHG and a chosen speed until back on path to avoid problems.
I should add that our SOPs require the input of best available info on winds during the descent, QNH and temp at destination and encourage regular reselection of the next WPT to update the winds in order to keep the path accurate. As always, one has to be very careful to check VNAV's actions after making any updates.
Our ops manual also mentions that you will see a CDU message warning of 'drag required' if an unexpected tailwind results in a significant increase in airspeed to maintain the path.
Unfortunately, it sounds like the scenario that caught you out. Company's reaction certainly seems OTT given their lack of guidance or SOPs.