Well, DPS underperforming is definitely a problem at this point, largely because our DPS are spending a lot of time dead and our tank swapping is clumsy to boot. We're fresh to the content and still learning it, so it's not as though we've hit a wall or anything. We'll get it with due practice, I have no doubt.

What I wasn't certain of is why even practiced parties would use their cooldowns on the chitin when it seems much more logical to use them on the real threat. From the answers in this thread, it seems that these are the reasons:
- If you can one-shot the chitin with cooldowns, don't worry, you have enough DPS to take down the Suna'wa even without cooldowns.
- Mount stacks make two consecutive mountings awkward.
- Bismarck gets another hit on the island, or two if you skip the second mounting to avoid stacks.

Seems like a decent explanation, and that's what I wanted to learn. Thanks, all!