It's the same as before minus the aggro combo imo. I hated using my aggro combo outsite of my opener because it was boring to do in stormblood (i was a drk main).
Gunbreaker already has 2 combos and sometimes has a lot of weaving to do (if you have a tankbuster while doing your continuation and having your dots to use). With gunbreaker i have already almost 3 full hotbars (https://imgur.com/pNzwRTP), it's perfect for me. Reducing the continuation combo cooldown would result in even more weaving, idk if it's a good idea.
For drk then yeah they can add some skills or 1 combo because right now it's the same thing other and other, theres no other combo or change of pace like gunbreaker.