Karin seems interesting because she brings something into CB that CB lacks, but instead brings it as an advantage.
The lack of cooldowns make the arena a lot more chaotic and brainless (only very specific units have cooldowns that matter, most doesn't have them, some like Haruka have cooldown = int, which is pointless to have the cooldown at that point), while in other games where there's cooldowns and/or reloads, you get rewarded for thinking ahead or taking risks rather than just holding fire all the time.
Karin's gimmick pretty much offers you less power for less downtimes, or more power but you have downtimes and "theoretically" slightly plan ahead instead of just mashing M1/2, but she offers way too many dashes for you to quickly get in, unload and get out to load her cannon again.
Pretty nice looking concept, and as usual, wasted.
I just wonder how people will deal with her cannon, considering that it's a copy/paste of TBG's (which in turn is a modified ctrl+V of Lisel's), which people say that it's bad (it's not bad, the users are), except with a gimmick, a debuff, less force on normal shots (gimmick might increase it or not) and more ammo (which doesn't really matter).