Well......um....yeah. (Wow, awesome way to start a post)
I think all the Kat hats (excluding the Black Kat Cowl) deserve a slight boost. First of all, lets have a look at their stats? No? Fine, I'll force you to >:) (Grabs the readers' head, smashes it into the computer screen)

Kat Hiss Cowl:
Split Normal and Shadow defense
Bomb Charge Time Reduction: Low
Bomb Damage Bonus: Low
Weakness against Shock and Curse
Resistance against Freeze

Kat Claw Cowl:
Split Normal and Shadow defense
Sword Attack Speed Increase: Low
Sword Damage Bonus: Low
Weakness against Shock and Curse
Resistance against Freeze

Kat Eye Cowl:
Split Normal and Shadow defense
Gun Attack Speed Increase: Low
Gun Damage Bonus:Low
Weakness against Shock and Curse
Resistance against Freeze

Phew /drink a cup of lemonade. Ok, now where were we? Ah, yes. Have a good look at the stats above, here, you can borrow my glasses /gives glasses to the reader (I don't actually wear any/need any :P). Now, lets have a look at some other hats (for bombers, swordmasters, and gunners respectively)

Shadowsun Stetson:
Split Normal and Shadow defense
Gun Damage Bonus:Medium
Poison Resistance

Skolver Cap:
Split Normal and Piercing defense
Sword Damage Bonus:Medium
Freeze Resistance

Volcanic Demo Helm
Split Normal and Elemental Defense
Bomb Charge Time Reduction:Medium
Fire Resistance

As you can see, these three hats give a larger boost in one aspect (damage bonus and CTR respectively), they all give resistance against one status, and have no negative-status-resists (I have no idea how to put that into proper words XD).
Now the big question is, why would you favor those Kat Cowls over these 3 hats?
Some may argue that the cowls and the hats (that I mentioned that is) are pretty much equal. Because Low+Low=Medium. Fine, I'll let you go on that one, but then why are the cowls weak against Curse and Shock? If anything, just remove those two weaknesses and you'll balance out everything a bit more.......... (If you've been able to read until here, congratulations! Because personally I think my English is horrible XD)

As you all probably no, the Cowl hats are only available (regarding you don't have the ancient pages) during the Katastrophic event. Besides, it takes time and energy to get those pages during the event...........Altogether, it takes 150 ancient pages to get the required materials to craft the 5* version of the Cowls. Ok, let's say you come across a Black Kat in EVERY 2 clockwork levels. Each black kat drops 3 ancient pages. So you'll have to run 100 clockwork levels to get 150 pages. 100 clockwork levels=1000 energy. Plus, the event is only around for 2 weeks (which seems like a lot, but if you are one of those people who is running on mist [or just happen to be very unlucky, like me], then it isn't)

But Papaya!(you say) You also have to earn crowns to obtain recipes for the normal hats! Won't you take up 1000 energy anyways? Well, lets have a look! To get all 4 recipes to craft a 5* helmet (or any other piece of equipment) you'll need 40k crowns. If you keep on spamming vana runs, you'll be able to earn that in about 6 runs. Each run requires 50 energy (regarding you don't need to use energy revives). 6 runs will cost you 300 energy. I'm quite sure that 1000 is greater than 300 :P. Plus, you don't have a deadline to earn 40k crowns, pages on the other hand......
(The exception for this is the gunner line hats..........you only need 39k crowns, but then again, its just a 1k difference)

Conclusion!(papaya roll please!)
/sleep
What, oh right, the conclusion...........Either, 1. Give the Cowls a buff in terms of CTR/DBI/ASI OR 2. Remove the negative-status-resists.

That's all for now! Thoughts?:3