1) All sets should be separate. Never assume one is broken when another even if they share the same mechanic, which would be the only time it would be more likely.
These do not share the same mechanic.
2) Queen's Elegance just buffs the light or heavy attack damage while Galerion's Revenge procs a debuff on the enemy.
Are you sure you actually fired a light attack when you think you clipped it and not just an ability? Timing can be tricky.
Yes I'm sure , you could even test it out for y'all self . Also its doesn't work with and without an Ability. Like you literary have to just click the light attack or do a full heavy attack for this set to proc