I personally tried to go back to Rogue Galaxy recently, and had a lot of trouble getting into it. You're right that Gambits would've made the gameplay better. The AI is rediculously stupid at times. There's also challenges that appear randomly, but they just aren't worth doing on your first time on a planet. The general combat, though, is rather annoying, IMO. You're attacks are limited in number and of course there's that weird guage thing that drains every time you attack, I guess it's a nice idea, so you don't just mash your way through every fight, but it does make battles longer than necessary, and I found that they quickly became tiresome. Which wouldn't be a problem if you didn't need to engage in lots of battles to level up your equipment so you can use them in the fusion process.
Of course, overall, it still feels like a good mix between the good ideas Star Ocean 3 and FFXII had, it's just that it didn't quite take all of them as far as they could've gone.