Not a fan of attrition-based gameplay myself.
Remember all those classic JRPGs from the 90s where you do not heal to full health after every battle? Players would have to stock up on 98372 healing potions just to keep their health topped up.
For rest-based abilities to work in POE, there would have to be limitations on how often you can replenish its use.
Using that one Fireball of Awesome Explosions in one fight isn't really a test of strategy and skill if you can use it every fight by resting before-hand.
In order for it to be a meaningful restriction, you would have to limit the way resting works. Maybe make it so you can't rest more than once in a day (who sleeps 8 hours, fights for 1hr, then sleeps another 8 hours?)
But if they made it this way then rest-based abilities become too underpowered, and they need to make it more powerful to compensate. But then it creates another problem of having a character who's not being utilized to the fullest in most fights, only going 100% in the more critical fights.
Rest-based systems don't make a game better or more challenging. It's just a design choice. What makes it challenging is how the devs design their encounters around the design.
There are other systems around:
MMOs use cooldown-based systems (you can use Skill X only once every Y seconds) Action RPGs use combo-based systems (you can only use Skill X after hitting with Skill A and Skill B and then Skill C). Back in the 90s, JRPG type limit-break systems were popular (You can use Skill X after killing Y number of enemies).
Of them all, I just happen to like attrition-based systems the least.