The backstabbing grapple of the assassin is inconsistant (I think?). When I play as the assassin or tank, I find tht it is random whether backstabs kill in one or not (against me or the other player) and it either does the same damage as a normal grapple or kills. Has anyone else noticed this or is it just me?
Players using armour endorsements will effect your outcome, a tank with gold armour only takes about 75% damage from a dagger back stab, a sword I think will kill or be very close.
As the previous poster stated, Armor endorsements can ruin your grapple kill. Just make sure to follow up your failed grapple with a Reload Dash and you might finish them off. If you find that the player in question will not die in a single grapple, either reload dash or shuriken them first, or just wait for them to get into a fight and take some damage.
There are few variables at play. The damage of the assassin grapple is dependent on whether you have a dagger or sword and whether it is a front or back grapple. You'll always do more damage if you can sneak up from behind. Tank's passive upgrade gives him more health which the target may or may not have. Finally the default Tank class the has Gold tier armor endorsement but custom Tanks may use something else. Depending on what combination of upgrades and endorsement both the Assassin and Tank have it may or may not be a one shot kill. Word of caution, as an Assassin never assume you'll one shot the Tank.
The one actual issue with the assassin grapple is that it is affected by lag far more than anything else.