A lot of crash reports on S6 too.
I only seem to crash when I lose the battle and there is a Slayer in the opposing line too.
However that observation is based on a very small number of battles!
Prior to using Slayer it's VERY rare that I have any crash issues (I know I'm very lucky with that!!!)
Hopefully there will be a fix soon!!
Edit: IPhone 6S Plus
Edit 2: Used in War this Morning and Crashed, No Slayer in opposing Line and Won so completely the opposite of what I had before! Joyful!