Razorfin Hunter is great if your creatures cannot attack (Ensnaring Bridge, etc.). It also kills key creatures (Goblin Welder, mirror match, etc.). It isn't very good if your meta is still Dragon and Keeper, so keep Voidmage Prodigy in.
My counters usually are:
4x Force of Will
3x Daze/Stifle
2x Stifle/Daze
1x Misdirection
