debuffs in GD gets pretty simple when you break it down:
general debuff rules (applies to more than just RR)
A: -%(minus symbol, important) stacks infinitely from different sources
B: %reduced, you get 1, highest applies (no minus symbol)
C: “flat”/n’th reduced, you get 1, highest applies
a+b+c goes together
^above rule apply to other debuffs too
like ex OA or DA shred
so since both Empyrion and War cry are type b, %reduced, no stacking, highest applies