So the current stealth mechanics are definitely powerful, and if you wanted to you could solo the game with a Gloomstalker 5/Assassin 7 (though Thief 7 would still be better most of the time) extremely easily.
I never really bothered with it after Act 1 though. The game gives abilities, items, and consumables that break the action economy and increase damage beyond what could be considered reasonable for the levels at play. These items/abilities are also much less tedious to use than all of the setup work that goes into positioning the party for the type of ambush situations you describe.
That means it mostly comes down to how you want to play it. You want to be a sneaky boy, great you can and the game even rewards you for that type of playstyle. I don’t really think it’s broken though, unless you happen to be of the opinion that the whole combat system is broken, since it seems to follow the game’s design philosophy of giving tools, a sandbox, and seeing what we make of it.
For a full stealth party I would run a Gloomstalker 5/Thief 7 Sharpshooter, Battlemaster 11/Rogue 1 TavernBrawler/Drunken Equipment, Draconic Sorcerer 11/Wizard or Cleric 1 Magic Missile caster, Tigerheart 8/Thief 4 DexGWM Cleave.