In regards to animation locking - this is not an excuse for the dagger to do 0 damage. The trade-off of damage for speed is still important, which is why I said it should be closer to 1/3rd a regular dagger.
The danger in animation locking someone with repeated stabs is vulnerability. You can be recoiled, blocked, massived (which has a longer range than the dagger btw). Not to mention you're doing minuscule damage and opening yourself up to the enemy team.
Also - animation locking someone with stabs itself, as stated in this thread, does futile damage on its own.