Here's my personal experience

Minato - 120 protections - still missing the mystery breakthrough

Kushina - 130 protects - missed getting chase, but got the frags for free from events to max sb her

Killer Bee (8 tails Jin) - 150 protects - missing standard BT

Roshi (edo tensei) - 150 protects missing passive + mystery (RNG was crap)

GNW madara - 300 protects missing standard (I almost wanted to rage quit after this)

So yeah... either give more protects or fix RNG