CS isn't that horribly imbalanced. In terms of matchups it's definitely much better than both CT and SSF4. The reason you see so many Litchis/Bangs/Ragnas in tournaments is because holy shit people want to win so they pick the best character. If Rachel/Nu/Arakune weren't in CT, everyone would just have played Jin instead, since he's basically 6/4 across the board. In fact, CS top tier is basically just three different CT Jins, insofar as the reason they are all top tier is because:
1) They deal more damage than average overall (5k meterless for Litchi, 4k meterless for Ragna, and 3-5k meterless for Bang depending on seals/FRKZ). Those three typically also have really good meter gain and can super pretty much whenever they want to (especially Litchi).
2) Their pokes are way too good, either in terms of priority, speed, utility, or damage. Bang gets 3k off 5A and Ragna gets 4k off 5B. Compare that to Hazama (who is A tier) who only gets like 2k off 5A and 3k off 5B.
3) They just have some sort of annoying BS. Litchi is self-explanatory, and Ragna's oki game ending in 22C/Berial reset is just too good. On the other hand, Bang has his vastly improved nail game and now he can turn the game into a ridiculous mixupfest with just two combos into FRKZ.
You can compare that to the CT top tier, which was just ridiculous zoning shutdown all day, and CS top tier looks a lot more manageable. I'd rather deal with Bang's 5A (where I can at least reach him) rather than spend half the round trying to close in on Nu only to have her push me back out with random D swords.