Specifically in tactical combat,  right click moves.  and if you're next to an enemy , right click attacks.

However if you're using an ability then you left click to select the ability and left click to attack/use skill.   Even if it's a melee attack.  

So sometimes you attack with the left button and sometimes with the right button and not much visual indication that you've got an ability selected leading you to occasionally use the wrong type of attack or nothing happened.  It's not a game killing bug, just an immersion breaker as you have to mentally figure out why you cant use the button, sure once you play a couple games it's second nature, but initially it's inconsistent until you train yourself to it.

Wouldn't it be better if the right mouse button was always the 'do something in the gameworld' button and the left button was 'interact with interface'?