If a velociraptor latches onto a player it will just float, won't follow the player but will still do damage.
It will stay in this state until killed.

If a velociraptor latches onto any other mob(including dinos) the target mob won't be able to do anything and the raptor will just keep attacking it until the mob is dead. So techically the velociraptor is the strongest dino currently in the game becouse it can even kill the T-rex and the Spino.
(i'm talking about a single raptor not a pack)