TBH I've never liked Vancian casting. It works in tabletop, but in game so far it's come down to spamming a sleep button. Oh no, Aloth ran out of spells again, better sleep in this dungeon surrounded by enemies even though it's the middle of the day. In all practicality it IS per encounter because you can just sleep between every fight, with a slight inconvenience - camping supplies/finding an inn is at most a bit irritating. It's not like dungeon enemies respawn, or at least I've never seen them do it. If I really need more spells I'll go through the irritating slog of retracing my steps, going to an inn, and finding my way back. The only thing encouraging to use less spells isn't strategy, it's annoyance.
I'm not especially fond of Vancian casting myself - even on the tabletop. (I actually went through the enormous effort of decoupling it for my current campaign world and made it into a mana system). (But that only changes the implementation of spells, not the strategic implications, mana points run just as much on the fifteen minute adventuring day.)
The problem is, it's only a self-imposed strategic limit. Only the people that want to basically roleplay it are the ones limited by it; even in IE games it was pretty trivial (if tedious) to circumnavigate. PoE actually only sort of partly took some of the irritiation out with the camping supplies... But as inns gave you bonuses, there was some benefit to the tedium of traipsing back out of the dungeon every time.
(And random-encounters-while-you-sleep to try and force people to not rest when they like doesn't really work, since if the PCs have stopped to rest, it's because they're out of combat powers. Throwing combat encounters at them to punish them while they're already week will only work if the DM is prepared to end the campaign by killing them, or the CRPG is going to reload (or game-over). There's only so much you can do with respawn or moving monsters around the dungeon too.)
On the other hand, I made it through more-or-less the entire of White March 1's dungeons on the strength of the then-per-encounter low-to-mid level spells; but part of the reason I stalled out until this week on WM2 was, I think, the dropping of that feature. So while it did mean that I rested less often, because I only burned my high-leve resources more sparingly, there were time when I didn't have to use them at all. (Conversely, outside Concelhaut's tower, when I went in at level 12, I was resting more or less after every fight.)
So... yeah. The problem is, basically, it's trying to do diametrically opposite things - have a limitation on resources and also having the abiity to refresh the resources whenever desired.
D&D 4E presents the same set of problems, with the mix of perencounter and daily powers. The early (official) modules taught us not to go wandering when low on resources, so for the next umpteen levels we regularly rested and caused the DM no end of problems; in the end, we made a gentleman's agreement we would aim to do four comabts between rest and use our resouces accordingy. (So anecdotally, even o the tabletop, someitmes the rest-limitation only works if the players agree to it.)
And on top of that, you have the trash mob/ boss battle issues as well, feeding directly into this, The more of the former you have, the more disposable resources you need. (Now, I tend to run games I write myself on largely a "trash mob to get the players settled in to the day session/all bioss battles thereafter." Preportedly, this is what Tides of Numenara is going too attempt to balance out the fact that turn-based combat can be really grindy and dull with trash mob fights.)
And about the only way to force people to divide out their resources (becaue otherwise, the designers have to take into account every fight will be treated like a boss fights by a not insignificant proportion of players) is to start having time-limits... But that itself tends to put unwanted pressure on people who want to take their time. (I particularly dislike them; one reason I have never finished Mask of the Betrayer was I just got sick of feeling like I had to rush through the entire game; especially when most of the companions were primary casters..)
There is no good answer, really.