I still REALLY think they should put emphasis on action economy in the books. Action economy and traits (especially ones that have cumulative negatives such as the slimes) can wildly affect the outcome of an encounter.
In scenarios like tonight, where the party is getting weaker and weaker, and the action economy of the enemies is multiplying, it throws all initial balance out the window. CR is a complicated one that's for sure.
Unfortunate JP got hit with the unforgiving d20 of fate 3 sessions in a row but that's D&D for you. I think it's important that everyone remembers that D&D boils down to randomness, every roll has the potential for euphoric success or catastrophic failure.
Looking forward for what's to come either way.