- Tithe points spent at start of turn (a)
- Blood Thirster arrives via Deep Strike - assume scatter as normal.
- As a FMC he arrives Swooping, cannot move or assault.
- Turn (a) + 1 he can move and switch to glide, still no assault.
- Turn (a) +2 he can assault.
So basically, unless GW come out with a FAQ specifically directed at KD and summoned creatures the rules of the game effectively make summoned Blood Thirsters a complete waste of points. With a Slaughtercult your better off spamming other stuff or going with Apocalyptic Fury and formation wide FNP.
Rules are rules but it can't be what the intent behind the rules are as it means in a 6 turn game a Blood Thirster summoned in Turn 5 will never see combat, in Turn 4 will only see combat in Turn 6 and in Turn 3 will only see combat in Turns 5 & 6. They can still shoot with their RNG 12" S6 Assault 1 Lash of Khorne but a Melta does the same job for less points.
Won't change my list as I'll still take one but will just adjust my tactics and spend Tithe points a lot earlier.