You always have to keep an eye on those damn Destruction locks. For me, watching Destruction locks is kind of like blaming the victim (I know that's wrong, but it isn't a problem when you have that mind set) you have to do everything in your power to stop them from completing a cast of CB, that way, you never suffer a spike in damage. Or if interruption is not possible, prepare your defensive cds (or your anus, whatever).
It's not any different in a BG, so why would an arena be different?