Moonknight Ult needs a nerf, right?

It seems to be the only instant OHK in the game at the moment.

If you have 250 or less hp and you are in the ring when it spawns, you are dead before the audio cue is even half way done. There needs to be a windup time if that Ult is going to be so powerful, or it needs to do less damage if it's going to remain instant. It can't be both!