To summarise The Kat Claw, Eye and Hiss sets (Swords, Guns, Bombs respectively) have a somewhat relative high cost of creation, Most of the Cost comes from the Cloak, Mail, Raiment (3*, 4*, 5* respectively). Understandably the event was released with the Idea of the players getting said sets during the period of several Kataclysmic Confrontation Events... But even so, after several of said events a lot of players haven't compleated even if they have farmed said event exhaustively.
I'm not going to minimize the prestige of getting said set, but also... the necessity for a change (yes, a lot of them have been suggested before, yes, the team is working on review some sets), What if the Cloak of said sets (3* Armour), would cost 1 Wicked Whisker to create, while the Mail and Raiment Didn't. That way You Do have to compleat the Dark Ritual and deal with the consequences, but not 6 times... (unless You Really want to).
The sets are quite well balanced, are pretty, and help with the variety of Gear in some cases... Yes mostly Overshadowed, because why would You do any of those sets for the same cost of the Black Kat set. Keep in mind, that I haven't said to change the Black Kat set in any form, I Do think that the ability to do Maximum Damage to Everything, Everywhere All the Time, Should Cost dearly.
Not only are the sets costly, but (using kat eye for reference as I am a gunslinger) rather weak. BK is fair, I'd argue too expensive but you do get the damage and movement speed with the cloak so it is possible to glass cannon with that. Unfortunately, kat eye has a cheaper alternative that can be acquired at any time and has better effects: Sacred grizzly shade.
I would like to suggest improving Claw Eye and Hiss Raiments to give Ctr, Asi and Damage medium or high (I will admit that's strong, but it is limited to one weapon type). Additionally, making the sets slightly cheaper would be very helpful because sure, they are meant to be legendary with a great challenge to get them. But given that you need to be near endgame to stand a chance, having motivation to do the dark ritual 6 times is quite ridiculous.
An additional slight change I'd suggest is making it possible to purchase wicked whiskers for a high number of ancient pages (something like 300).