Should regenerate - they're likely going just for the leaves (desperate when it's holly!) rather than nipping off pieces of branch. For some reason (and not deer) my new 2007 planted holly dropped all its leaves that fall. It came back like gangbusters spring of 2008.

Next fall, if it's small enough to be practical, you might cage the holly in chickenwire or wrap it in burlap. Deer don't bother even when desperate when you make it a bit difficult for them.