IMO he should be able to be stasis'd but instead of being totally worthless I though he just should lose his y ability along without being able to move...This would stop people from just making 1 or 2 vamps to deal with him because he would be able to just shoot them down decently fast and it would balance out his late game especially now that his flying upgrade is a huge speed improvement.  

Easy thing to do though is just bring some vamps of your own.  Not sure but I think you can still teleport units in when you get stasis'd so if the guy only have 1 or 2 vamps make 1 or 2 yourself and when he stasis' you  just scan them in and waaalllaaaa you are free and he has a dead vamp.