Thanks for the Wiki. I had to play with power auras but could eventually get all 3 to stack properly using only 4 auras (none of which needed to be disabled). Here's how I did it:
Aura 1: Exploit Weakness as trigger buff (nothing in ID slot) as Colour 1 (or image 1 etc.)
Aura 2: Arcane Empowerment as trigger buff (with 1 (or the appropriate ID) in ID slot) as Colour 2
Aura 3: Culling the Herd as trigger buff (with 1 (or the appropriate ID) in ID slot) as Colour 2
Aura 4: Exploit Weakness as trigger buff (with 2/3 (or appropriate IDs separated by a /) in ID slot) as Colour 3
This will make sure that Empowered and Culling only go off if exploit is up and allows you to monitor the +dmg debuffs in stacking order Exploit; Exploit +1; and Exploit +2.
Making Empower and Culling as the triggers (vs. Exploit) allows for fewer auras to be created (and subsequently disabled).
Hope someone else finds this useful.
Edit: You wouldn't know English was my first language. I'm a terrible writer.
Edit 2: Oops "Arcane Empowerment" not "Empowered Weakness" which as a term is rather interesting. Ty to the post below for pointing it out
