So... just to confirm.... even though the mouse is being used to attack, the direction in which you attack is not related in any way to where your mouse cursor is?
If that's the case then please DON'T USE THE MOUSE TO ATTACK! It's an unnecessarily confusing input method that makes it feel like the controls should be different than they are. A keyboard key would make it both a more intuitive interface because it wouldn't provide the wrong "affordance" that the mouse provides by suggesting you can aim! It also is a bad experience on a laptop with a touchpad to require lots of clicking (for various reasons).