[@vancexentan] Actually, Ibaraki is weaker, and she's already a Beserker. Ibaraki's stats are B, A+, C, C, B. Shuten has A, B, B, A+, D. With a Mad Enhancement boost, it's pretty easy to put Shuten in A+, A, A, A+, D stats. And her battle continuation lets her fight even if she loses her head. Shuten is a super scary Berserker. And her poison is pretty much instant death. 

Beowulf is a terrifying Berseker too. Because even without Mad Enhancement he has A, A, C, D, A for his base stats. And he can easily push higher than that with his personal skill, Berserk basically giving him the ability to go from no Mad Enhancement to A Mad Enhancement with his stats pushing A+ A+, A, D, A.

A lot of Berserkers in Grand Order are insanely overpowered, since none of them are Screamzerkers either. So they tend to have their sanity to at least some extent, or a skill that lets them preserve it.