Well in theory, they wouldn't have to change any of the normal client/server stuff for this.

The full damage of a three hit animation can still be applied at the same time. All that would need to change is how the client displays it to the player.

Most of it would depend on your camera angle, and mob position relative to you.

The rest should just be timing and math.

The one exception I can think of is if an animation connects prior to when its damage is registered for calculations.