I’m still working some things out, but I’ve figured out a basic mechanic for simultaneously making enemies a bigger threat to the party even while the players technically have access to more powerful effects, limiting the usefulness of limited-resource powers without nerfing them, and making basic powers more attractive.
The idea is “Surge,” which I think some other independent roleplaying systems have already worked out, which serves as a representative for the momentum or “tempo” of an encounter. Each time a player or a particularly powerful enemy uses a limited-resource power (Encounter- or “Daily-“equivalent powers), Surge increases.
Enemies, by default, add Surge to their attacks and damage, while the player characters must utilize certain other powers to gain advantage of Surge (though their use of it is more versatile). Thus, if the player characters try to “nuke” all of the enemy creatures in the first round of combat, the monsters get that much tougher.
You could think of it as a kind of “drama inhibitor/booster” for when the players want to speed things to a dramatic conclusion. For the time being, I’m thinking that Surge caps out at a “plus six,” incrementing with each limited-resource power used, so it’s possible for a full party to max it out in one round, but a lone character taking longer.
If I decide to reinstate critical hits in some form, I’m thinking their role will be specifically to up the tempo as part of their effect. Sure, you might get some sort of damage boost, but only if you’re willing to accept the consequences for creating such a dire threat to your enemies. It’s an interesting idea for me to toy around with.