Is the mace windu event busted?

My Aphra potency set was heavily used for this unlock.

You seem to be misunderstanding how mods work.  You're confusing the picture on the mod as working like the primary buff.  The pictures only give a bonus if you complete a set.  2/4/6 mods of most sets.  4 mods for speed, offence and crit damage.  1 of a type gives no bonus. 3 of a type only gives a bonus of 2.  Less than 4 CD or offence mods won't do anything for you at all.