How hard is this Limit Break as opposed to doing it with another job?
I'd say COR is one of the easier G5 fights, so don't be too afraid of it. It's true that getting a testimony is a bit more of a pain than other jobs, but if you go in prepared I wouldn't expect to need more than a couple trys (hopefully you'll win on the first one).
COR just has so many tools for quick damage on this fight. With Quick Draws, resets from Random Deal and Wild Card, and the ability to get a couple quick Slug Shots off by using (1) Opo-opo Necklace and sleep potions to start with over 100tp, and (2) an Icarus Wing mid-fight... you should be good.
I went 1/2, and only lost my first one due to some exceptionally bad luck (got rocked for 2 crits, missed my Slug Shot that would have killed him, and kinda fumbled around with QDs). Went back for a second attempt and won easily.
A couple other tips:
- practice first on the Pulling the Strings solo ENM, as it's essentially the same strategy
- A Blink Band helps get you a few free hits