I think the taunt would only fit in if it damaged enemies. The animation suggests a backstab, but since it would be too overpowered, having it only backstab when in the imediate vicinity is a great solution. The damage based on distance can be added, but I think it would be quite useless or unbalanced. All in all, I believe that the taunt should only backstab when almost close enough to stab. On top of that it should only affect one person at a time.