SOME destroyers, not all are bugged.
I know that because i was dealing with their zone layouts in NSM mod. So in example the fubuki and shiratsuyu destroyers are both using zones from battleships and their armorlevel is bugged making them having infinite armor on some parts.
check this link:
http://www.subsim.com/radioroom/showpost.php?p=618297&postcount=355
And download this mod:
http://www.subsim.com/radioroom/showthread.php?t=120269
These bugs are all fixed there and entire damage system is reworked. Make sure to read the readme.