Chiaki is a steal. She gives the ressers a very solid support model she is almost like the Nurse v2.0, I'll just go through a couple of useful things that may be overlooked (yes she gets better with Yan Lo but she works nicely for Nicodem and Seamus as well)
1. The Light - bascially friendly models close to her gain regen 1 (+ if they already have regen). Its not much but I like regen
2. Pull of the Grave - counters a lot of models and will generally find a lot of use against Arcanists, Neverborn and other Ressers. A Df 12 duel is going to burn through deck or hand which adds up to increased pressure
3. Cleanse Spirits - Witchlings are considered on e of the best models in the game, they remove counters and effects that target one model, this removes them on multiple models. This ability in itself is golden
4. Board Control with Living Memories and Purity. Controlling the board is so important and these give another layer of control.
5. She is only 5ss! that is a great price for such a support model who really helps the rest of the crew perform