I don't want to derail the thread, but for you and
@doctorbadwolf and any others:
Its not so much that the game "broke", per se (probably a bit overdramatic on my part). It was more a combination of multiple small things:
1) Pacing: I wasn't running a 6-8 encounter day, the party was able to "nova" just about every BBEG, and most enemies, unless super deadly (which then I had to walk back from TPKs) were cakewalks.
2) Characters:
Thief/Warlock multi (I understand multi is usually suboptimal), but the combination of thief subclass (Swashbuckler) movement, sneak attack, plus Warlock Chain Pact, Imp (fly, invisibility, ability to see in darkness), Genie Patron (ring to hop into to escape combat and invisible flying homunculus flies away with it) alongside devilsight and darkness, plus Eldritch Blast spam.
Evoker, which was pretty basic, but the ability to throw AOEs into any situation and avoid other players while hanging out in the back, plus spammed cantrips for damage was powerful.
Arcane Archer (not super helpful, but the occasional grasping arrow and tracking arrow were situationally good),
Cleric (standard - spiritual hammer, sacred flame, spirit guardians, healing word) and
Cleric/sorcerer (Twilight Cleric, plus sorcerer which wasn't that noticeable, but twilight was great).
It was a huge range of abilities, even without any kind of front line fighter, that could spam cantrips and not use resources against low level threats, and could nuke 12+ level NPC casters and other big monsters in one to two rounds. And that was with utilizing spellcasters with hold person, and attempts at counterspell, yugoloths when the campaign area dictated it, mixed groups of smaller and tougher., etc.