"Don't play melee characters" isn't really a solution though, it's just avoiding the issue.
Its a ridiculously easy series of fights between the ability to ambush the entire pack (can kill like four with two Shatters, PC + Wyll), ability to kill all the Hyenas without aggro'ing anything with stealth, and then the option to tadpole the big bad.
That said: Enemy stats, dice rolls, damage rolls, high ground, surfaces, etc etc that vary wildly from the 5e ruleset break the balance of what is supposed to be a 5e game, and thats the core issue OP is experiencing, it just happens to be dressed as a bunch of gnolls right now. They basically introduced these functions and then had to compensate with the bonus actions they gave us.
It feels really silly, and I'd prefer they just get rid of inflated enemy stats and abilities/surfaces, fix dice rolls (Probably a bug that will be fixed lol), and make bonus actions/jumping function how its intended in 5e.
One problem of this fight so far is that they've introduced at least one status effect I can't find anywhere in 5E, which is "Soulblight" or something like that. It makes the target unable to use bonus actions or reactions, and one of the gnoll casts it almost constantly so it's either some kind of made up gnoll cantrip or this gnoll has more spell slots than I've ever seen. Also really doesn't help that the boss has the most insane weapon I've ever seen, this thing is some kind of flail that, last hit I took, did 12 physical damage (dunno what kind, cause it was overshadowed by) and 30(!!!!) of some kind of magic damage, psychic I believe. Edit: got myself a new record for damage from Flind's weapon, 17 bludgeoning and a whopping 47 psychic.
