Mercenary & Warrior Mouse LB RB &/or QWERT keys to attack with?

Mercenary & Warrior Mouse LB RB &/or QWERT keys to attack with?

I need some information or help, something doesnt make sense.
I will begin with the Mercenary & I will try to make it as simple as possible.

I use Mouse Buttons to move around on the map & to attack the minions/monsters.

Mercenary
Mouse Left Button, I have "Punch".
Mouse Right Button is where I can choose to "load / replace" either...
Q = Load Armour Piercing Rounds
or
W = Load Permafrost Bolts
or
E = Load Fragmentation Rounds.
So if I press the key "W = Load Permafrost Bolts", I can use my Mouse right button to fire Permafrost bolts.
That part I amazing & love it.


Now to the Warrior


Warrior
Mouse Left Button, I have Punch
Mouse Right Button, I have Mace Strike
On the keys QWE I have.
Q = Armour Breaker
&
W = Rolling Slam
&
E = Shield Charge

This is where it gets annoying.
If I want to "Load / Replace" the Mace Strike on my Mouse Right Button with E = Shield Charge. It does not "Load / Replace" the Mace Strike on my Mouse Right Button by pressing E = Shield Charge, it acts instead.
So my question is, is there a setting to change that? so the warrior skills can be replaced instead of acting while pressing QWE.