Arena 1/2 or focus gripping casts for the sake of interrupting a crucial cast and not using it to interrupt any cast is important. I like to see how dks kick or interrupt, and if I get kicked on a non essential cast while I’m feeling them out (or any dps for that matter), I know where to proceed.
Can’t really give dk specific advice, but just from the pov of going against them.
Proper usage of AMS is also important and cof uptime is also ideal.