You are right its 30%.
Berserker and disciplined strikes offer alot of hit to crit conversion so you can get away with lowering your accuracy a bit.
I think it affects you more in the beginning of the game since she modal takes off a flat 10 acc when you only have only 40 acc right at the start compared to 115 acc at the end of the game.
I also really like sanguine greatsword since it makes your mule kicks super accurate. Great fun to play pingpong with bosses.
Sanguine is kinda hard'ish to get though.