Please don't use left-click for attack when there's no aiming involved. Everyone seems to be doing this now for some reason, and it's a terrible UX. The mouse only makes sense to use when cursor positioning is involved (including aiming weapons, etc). Using it only because it has a button on it is... inappropriate. I wish I knew what's driving this recent trend so I could cut it off at the source.
There are several traditional keyboard keys that work perfectly fine and make a game more portable to laptops that may not have a mouse connected and can have terrible experiences with trying to use trackpads simultaneously with keyboard.