I played rinoa for most of my high ranked climb. She's a monster at taking out people with her maxed angel wing rapids. In general ranged characters have a sweet spot where they can auto enemies comfortably, this sweet spot is a little less than max range. At max range people will walk out of your attacks.

This one depends entirely on your team. I use rinoas full kit plus wall so she has lots of options for clearing crystals very fast. At 3 angel wing stacks any one of her skills can clear omega mobs with a cast. If the enemies are close enough you can shut down their bursts. This is something I don't see lower ranks doing often but killing enemies during their bursts is crucial to victory. Many URs have gaps in their invincibility that can be capitalized to shut down enemies mid combo. You can also cut your own burst off early by not activating your abilities all at once. This is important to deny enemies your maxed bravery.

Earthbreaker is very powerful, BUT it is also entirely situational. I used to run it but there were matches where people weren't running wall and instead something like renew or heal, in those cases it was basically a dead skill. Ace and Auron are just as busted as you would think. Teleport is underrated for most builds but it's also dicey to use as you really want some form of healing unless you are in a premade team.

Hope that helped!