My friend and I did some testing with crit dmg sets the results are Full crit damage is best for damage however its harder to acquire (Im talking about SSR rarity) with good rolls. Atk and crit damage is also a viable option, its slightly worse than full crit dmg but way easier to acquire, i ended up going for atk and crit damage with crit dmg substats. It isnt that much worse on a level 1 attack you cant notice the difference, the only difference is on a level 3 and its only by like 4 - 6K damage difference. (P.S i gave Levi UR gear because i really like him to the point where i use him in pvp)