I think there is universal agreement that the new batch of gear and buffs are all out of whack. Namely:
Black Kat Cowl is ridiculously overpowered? (DMG high, MSI low)
Other Kat Cowls aren't sufficiently powerful? (weapon-type DMG low, ASI/CTR low)
Chaos Set was buffed too far? (DMG, CTR med)
The rare Kat hat is definitely taking things a little too far with universal DMG high, something that even max negative status wouldn't balance. I'd give it universal DMG/ASI/MSI low and medium negative resists (like Chaos), making it powerful but not freakishly so (since its bonuses would now be spread over a variety of categories). The fact that it is a random rare-drop (thankfully not as rare as Darkfang) should also mean it doesn't provide overpowering bonuses, for the sake of balance. Even if it were made non-random (like shadow lair equipment) I would still argue medium DMG is too high.
Along similar lines, the normal Kat hats could provide weapon specific DMG medium and ASI (CTR for bombs) low, with a medium curse weakness, and a medium type specific weakness, and a max type specific resistance. (low ASI/CTR at 3*, add low DMG at 4*) Depending on how we want it to be balanced, the weakness/resistance can be tailored to actively help or hinder that type of weapon user- for example, shock is extremely dangerous to bombers; freeze is bad for mobility-dependent gunners. This would make them on par with existing gear, providing a +3 to a weapon type with some weaknesses.
Chaos Set a glass cannon? How about a universal DMG/ASI/CTR low? Since all weapons gain CTR medium at heat level 10, a full Chaos set will start you at DMG/ASI med, CTR vhigh; a pair of trinkets and a shield (we do need more weapon buffing shields) will allow you to max the weapon type of your choice, before considering UVs. Personally I think the previous Chaos set (DMG/CTR low) was only mildly underpowered. I think devs should be wary of universal bonuses- weren't they trying to encourage people to make more armor sets? One only needs to look at the Swiftstrike Buckler for evidence that large universal bonuses tend to be unbalancing. Any sufficiently advanced player uses SSB as a key part of their arsenal, particularly gunners who have no gun-specific shield. This is despite the fact that they are only 3* and have very poor defense in T3.