So I threw some encounters together, quickly invented a couple of traps(I remember being surprised that there weren't any traps with a CR on the order of my party in the DMG), and fired up the game. First encounter: a horde of skeletons! Enough to make for a CR of 14, to give the characters a chance to show off without burning through too many of their resources. They opened the door, saw the writhing mass of bones, and rolled initiative. Druid is up first, he fires off a good-sized area damage spell.
A really good-sized area damage spell.
An area damage spell big enough to fill the room.
And that's it for the skeletons. Minimum damage with a successful save is still sufficient to kill them off. No showboating, no people behaving awesomely because there's only a tiny risk, just the druid naming a spell and the enemies keeling over.
This wasn't the only encounter that didn't go as I'd expected. The CR 16 encounter(a couple of golems) took forever, because the golems I'd chosen had some strange immunities I hadn't accounted for. Those selfsame immunities severely restricted the party's options, so only the first three rounds were interesting. The party circumnavigated my traps with very little expenditure of resources, because they had mobility options that rendered the traps irrelevant. And the CR 17 dragon at the end of the dungeon destroyed the party almost as quickly as the druid had taken out the skeletons.