Kait is good against all but the Kestrel(kind of) and Swarmak. The latter being due to the EXTREME amount of health the boss has. Matriarch is more a matter of being able to get behind and being able to shoot undisturbed. And maybe Guardians/Sentinels are a problem for her, due to their shield. But there is still reliance on JD overall. Or people just want him too much because of the ridiculous damage he deals, especially once you’ve maxed out or leveled Razor Hail to a certain point on him.
But still, I do agree this Horde is not balanced well. A lot of it requires on having different characters(eg Kait and Jack with Jack perma healbeaming Kait until the wave is over or he can fetch weapons for the Forge, or Marcus combining his ult with a Fahz for headshots) working together which is extremely absent in even Custom matches. Playing Kait on higher difficulties(esp with the extra damage modifier) without having a Jack healing you all the time is really annoying, especially once you’ve passed wave 30. She deals less damage while being restricted to mostly close range and kind of mid range with the Overkill and Gnasher, and relies on having a Jack using faster healing, and possibly healing distance, to be able to keep firing effectively. In 5 Horde, not even blind firing your weapons works to keep you safe. They still hit you anyway. Almost every time I have played her on Insane and upwards, I was outdamaged by JD due to his range advantage at some point beyond the early waves, didn’t get healed by Jack much unless he was reviving players from range, and after wave 30 would have real problems getting any hits or reliable damage in without having to expose myself a lot and unnecessarily. Just isn’t fun. But while I like doing explosives, the way JD plays out often feels very mindless even using a varied set of weapons over only 4 Lancer GLs. Kait is somewhat less worse on that regard. You at least have to do more than point in the general direction of an enemy to hit them with your Very tries”
Meanwhile, once JD has a locker, he literally needs no one else to do as much damage as he possibly can, from any range. I’ve had the argument that he’s way too OP countered by him not being useful in close quarters, but he’s not if you have any clue how you should use an explosive weapon when enemies are closer to you, doesn’t require perma healing from Jack and can deal damage at pretty much any range all the while having even higher damage potential than Kait, or anyone else on the team.