I've fought cassie 3 times in my last 5ish lockouts. Every spawn we've had was blizzards + morbols (and that one zombie that spawns inevitably gets aggrod by the train lol) as far as I was aware.

Don't know if the bunnies help. Theres usually at least one group of people farming the FATEs so its kind of hard to gauge if they're speeding things along.