i dont understand the ability at all, i see that it causes x5 bleeding effect, but it doesnt do very much damage. every button i press does only one damage, including the finisher. is the only purpose of the ability to cause bleeding effect, or does it do really nice damage if its done right? thanks for the info.

What does the ability look like when you do it? If you're seeing the clones fall down on the ground, they're not performing the ability correctly. When the clones appear on screen, you should press the directional input (WASD on PC, or the analog stick on a controller) in the direction the clone is facing... so for instance, if the clone pops in on the left and is moving right, you quickly press right. If you're unsure, it's usually the direction their pupils are facing. This causes them to slash in that direction.

Some enemies are strong against it until you break that defence down.  Usually if you gross them out, or do a defence down ability on them, you will see the true damage.  At end game each slash was doing 2-4k on normal mobs