The autoattack delay timer keeps counting down, even when you're performing combat arts. If you were using a low-delay weapon, like a delay=1.2 dagger, it would be possible to lose attacks when performing a long CA. But with our high-delay bows, at worst you'll just delay your next AA shot a little. In short, there's no reason not to use CAs.I'm not so sure about queueing up combat arts, though. I believe that if you queue a 2nd CA while still activating the first, your autoattack doesn't get a chance to fire inbetween.