Under no circumstances should there be any degree of invincibility or damage reduction based on an animation in progress, especially in regards to attack animations. If anything, concentrated fire on Preds should knock them out of quick claim animations. Quick claims also should only be applicable to dead humans, not Fireteam members in a downed/bleedout state.
Also, stealth kills should apply as they currently are implemented. Giving the Predator immediate access to stealth kills from beginning of the match is absurd.