Currently the best set at 75 with buffs at maximum subs are the following combinations.
ATK and CD set is 20% atk from set, 20% CD from set, 7 CD subs is 42% and 3 atk is 9%. so total is 29% atk and 62% CD.
Full CD set = 60% CD and full atk subs is 30% atk
Efficiency is calculated based off Spike Crit Damage 2x passive with Hellbram and Gowther buff. Subject to change when Deriri release. DO NOT REROLL HIGH ROLL GEAR. Build another piece of gear if you want to build for efficiency.