Despite the use of a $20 word (which honestly I don't even know how diegesis applies), I am not actively hostile nor do I control the narrative flow of the game. Yet I don't find it that hard to balance things out.
You must artificially ensure that the opposition is timed juuuuuust perfectly so three hours of resting never ever causes problems (otherwise you punish those people
far more than you punish the long-resters), but always so that the time pressure makes long-resting so risky it should never be done unless it can't be avoided anymore. That's not grounding things in what really exists in the world. That's tailoring opposition to suit the mechanical needs of the game. The opposition doesn't exist because it needs to be that way to make sense in world. It exists that way so that it can counter the game design that made spellcasters powerful unless intentionally countered.
Assuming you aren't also catching your allies, assuming they're all approaching from the same direction, assuming that this is an indoor location that is fireproof, on and on and on.
1: Most Wizards don't care, and Evokers genuinely couldn't care less.
2: You literally only need three people within a 20' radius, or two as long as at least one fails the save. This is not a difficult thing to achieve, even if the only come from one side.
3: Why indoor? That's completely irrelevant. I was actually imagining an
outdoor location, like the fight in Hussar's 5e game recently where we had three bandits attack from the front, three from behind, and a few weak ones scattered amongst the trees.
Buildings made of wood aren't flammable? Trees? The McGuffin the party needs to retrieve?
Most adventures occur in stone buildings (castles, temples, dungeons, etc.), caves, ruins (where no one cares that you set a wooden thing on fire), or wilderness areas. Only the last is
potentially a risk. A six-second
fireball is not going to set a rainforest on fire. It probably won't even set most ordinary forests on fire. You are creating an unrealism (forests so prone to lighting ablaze, a single storm could make them disappear in a puff of smoke) solely to counter the power of spellcasters. Very few combats actually occur
inside a wooden building.
Assumes that you know what you're going to be facing and then have time to take a long rest.
Not at all. I've personally prepared such spells and never once encountered something that resisted both. Even if I had,
chromatic orb is your friend.
Apparently you've never had a fighter using sharpshooter or GWM.
Nope! Too many people ban them for being OP, or intentionally avoid them because they're boring.
I think there should be options for spell and resource recovery based on the type of game you play, but even 4 fights per day can tax a wizard's resources.
Only if the Wizard is being utterly profligate with useless puff spells. Which isn't really relevant as a rebuttal.