@ the basic attack (ranged attack/Melee Attack) If auto-attacking is out of the question, how bout a keybind for the right mouse key. Have a customisable slot for our abilities (We can put .. auto attack for melee in the slot on our ranged bar) or the otherway around.
We can put what ever spell or ability we want in either slot which is bound to our mouse. When you press that key on the mouse (non-direction choosing) it uses the ability. So we could have hemorhage on the right mouse button, and the shadow arrow on left so you can use them easier and take up less room on your action bar in order to have healing/beneficial spells down there too so you dont have to press Z to switch tabs.
I would put the most commonly used spells on my mouse binds.
Similar to Torchlight's combat bars for the mouse, if you don't really know what im talking about