Was a coincidence, I was currently writing about our new Knave 2e one shot for the Knave 2e Jam. 7 monster for 2 players is a lot! Did they use a bludgeoning weapon? Because thats a general problem with the resistance/vulnerability design of DnD. It is very hard to balance the stat block in a way so the monster has enough Hit points to be fun fight when the players exploit the vulnerability and also not a overkill if they don't. The monster needs to be defeat able for players who attack it with resistant damage types, too. It needs to be a very hard fight but it needs to be possible. So thats the dilemma in that situation, i hope thats understandable :)
Now I am also intrigued, how did they do against the final boss? Did they directly focus the chest ? Also did the "action fight oriented" boss work well ?