I believe that the dragoon needs this rework for two reasons:

1.Too many buttons
I think it's clear that it's about ease of use and gameplay. The drg has three(!) combos that need to be kept on the panel. It's absolutely inconvenient. They need to simplify the first two combos on single target, making the debuff a bonus for a regular three-button combo, and make the 2nd combo aoe damage with two or three buttons. This will greatly simplify unnecessary management and make the gameplay much more convenient.
Those buttons that are pressed after a certain combo must be combined into one, changing depending on the applied standard combo.
The Life Surge is also unnecessary management. It must be used at the end of the combo, otherwise it will be practically useless. I constantly forget about it, sometimes on purpose, simply because it's inconvenient. The damage boost is negligible on the big picture. And this thing with "use [skillname] to make [skillname] work and then [skillname] will change to [skillname]" in the 80-90 lvls? Again, unnecessary management.
Also I would make it so that more abilities require a gauge to work.

I would single out "unnecessary management" as a separate reason, that's how big the problem is.

2.Unimpressive effects
No, this is not a quibble nor bias, this is a fact based on comparison. All classes, without exception, you can feel the might from abilities their use, take anyone - the paladin puts up walls and crap with hefty swords from heaven, healers shine brighter with each level, casters and even other melee look more advantageous. Not to mention the SMN or the DRK. Everyone has something that makes them stand out and it feels like these abilities are high-level abilities. Yes, at lvl 90 there is little variety, like red mage has a nuke in one direction. But what a nuke! So bright and powerful. Or the machinist with, yes, it's just a saw, but this is along with a damn robot with, like, ten abilities running around.
All this looks more advantageous than a poor dragoon: lvl 70 - Geirskogul 2 with an eye. 74 lvl - jump, but blue. 90 lvl - two little heads which are barely noticeable. Out of all, the stardiver looks like a winning one, but in my opinion he is the only one like that. And it's a Dragoon, the one with the power of dragons. How can this be so un-climactic?

I think these are the main reasons why this class deserves a rework. I mained it from level 1 to level 70, I liked it, but only until I returned to it recently and realized to myself "and THAT I have been maining for HOW LONG?"

I understand that I could hurt feelings of those who love the drg for what he is, but I strongly believe that his current condition can be improved. Yes, I played as an AST, I didn't like it, but only due to the fact that healers are simply not my thing.
I know how players can feel. I love to play DRK, this is my second main and I would rebel if they decided to change it.