For starters, FL4K - who is already considered to be the strongest and most popular playable Vault Hunter in the game right now - has been given a significant buff, but not even in the areas where they're weakest (namely with regard to pet health and damage output).
Instead, Gearbox has given FL4K's "Rakk Attack" ability a 100% status effect chance, while also increasing their Barbaric Yawp perk stats (which enhances the power of Pet Bonuses) by 100%. If that all sounds like Eridian to you, rest assured it won't to the long-term FL4K mains, who I'm sure will be delighted to hear their favourite character has become even more viable for Borderlands 3's end-game solo runs.
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Outside of FL4K's changes, Moze's Means of Destruction perk, which has a chance to add a grenade to the character's inventory whenever she deals splash damage, has been nerfed with a re-trigger delay of 2 seconds, to prevent players from continuing to exploit the ability for infinite grenades.
As for bosses, Gigamind's health has been reduced, as has Billy the Anointed's, while Katagawa Ball is no longer able to regenerate his shields. While the latter two tweaks make sense, seeing as they make for some of the toughest bosses in the game, the Gigamind nerf seems like an odd change.
The early game boss has quickly become a go-to loot farm for high level Vault Hunters, since his health was already easy to melt through, even on the first encounter. In any case, there are a couple of other smaller, miscellaneous changes that can be read about in the full set of Borderlands 3 patch notes on Gearbox's website here, so do check them out if you're looking for ways to pass the time until the upcoming Bloody Harvest event for Halloween.