You can make some encounters larger and increase variety is my point. If everything is 1-3 big enemies/5-6 medium enemies/10 small enemies, it's basically just predictable.
Anyway, I think the whole thing gets thrown off this way. If spells are weaker, cantrips become pointless, and you'll never use them because you'll rest spam, which you're incentivized to do because you have to use your stronger spells. Then you're long rest spamming and the warlock is now a pointless class, just as one example, because infinite long rest wizard is just more powerful.
There is a reason why in turn-based games there are practically no fights with a lot of enemies.
Each enemy added makes the fight longer. In a turn-based game, each enemy needs its own turn to move, so the more of them there are, the longer you have to wait for your own turn.
Watching your enemies move for a few minutes while waiting for your 10 second turn is definitely not fun.
Even if the AI was running instantaneously, the motion and / or attack animation still needs to appear.
