I run the adventures as written, for a group of standard, non-optimized characters. The worst thing is a slug fest where they can't die and can't achieve their objective either (which has happened several times in Rime of the Frostmaiden).It sounds like you need to be drastically increasing the level of your encounters?
Or put in secondary challenges within the encounters to increase both the challenge and interest /fun level.
Was your paladin wearing armor? Attempting to fight without any access to healing?Like my paladin, who was around 6th or 7th level when he was ripped apart by gnolls.
Fighting a paladin in my group, that gnoll would need a 15-16 to hit and do a scratch of 4 HP damage even if a lucky shot landed.
Sure, a horde of gnolls could do it if the paladin had no backup and refused to fight back.
But in general, monster ACs are way too low, attack bonuses are too low, and damage output is too low.