Diagnosing a dead beehive that you've never seen is a bit tricky, but I am
surprised that nobody (besides myself) has considered tracheal mites a likely
probable cause.  The symptoms (hive dies in winter with lots of honey) sure
sound a lot like the tracheal mite kills I have seen (including some of my
own when tracheal mites were the only kind we had to worry about).
 
My experience with Varroa kills has been that they happen during the summer,
and are noteworthy because the hive "crashes" from full strength to dead over
roughly a two week period.
 
Anyway, at present U.S. beekeepers have to use independent treatments for
both, even though they may both be used at the same time.  Treat for just one
mite, and the other will get you.
 
W. G. Miller
Gaithersburg, MD