Shizuka should be pretty good because she has fairly good stats to perform as offtank/sweeper (500+ def and sufficient hp post-AW). she should be the only samurai you bother about if you have her.
I actually have (and quite like) chizuru. I honestly think that shes one of the better samurais , since , whiel still a samurai (and therefore sitautional) , she is really good when her niche apears