I dont have an Arcanist crew myself but I have played with Kirai before, the thing she hates most is blast markers. If she is surrounded by Seishin they will pop.
Izamu is tough, I like having him in my Yan Lo crew and he kicks butt, sadly in some games he has not earned his points, my ability to flip low cards mean he aint so tough. Like all big guys, take him down with lots of small hits from a distance.Spirit and armour still takes at least 1 wound per hit.