Actually, bringing up the number of enemies and power of enemies is not only valid, but it is extremely valid. They are all equally part of the balancing act. Changing one affects the others significantly.
- If you have less and/or less powerful enemies, you need rest less to recover from combat.
- If you have more enemies or more powerful enemies, you need to rest more to reover from combat.
This creates a new challenge that goes beyond defeating a single encounter. It is defeating an entire dungeon - or leg of the adventure. This, sadly, is something that many RPGs actually lack.
Rising to this challenge is the same as rising to the challenge of kiling an ogre, but your strategy will be different. It will need to be bigger. Defeating that ogre is now just a small part of that larger strategy and how you did it now becomes important. Conservation of firepower is not something to be tossed aside. As with spells, you also don't want your fighter's health to expire too quickly by taking to much damage in every encounter. Managing health may be more straightforward - use better armor. Picking the right spells at the right time, using only what is necessary, and knowing when your spells become necessary is definitely a higher level of gameplay that may take a little getting used to, granted.
I actually do use wizards, they are great, I also rarely need them to rest more often than the fighters in the party because I strategize to use spells in step with how hard my front line is getting hit. Even on PoTD, I generally have 2 and almost never go below 1 camping supplies on hand.
If your idea of a wizard is constantly slinging super powered spells every chance they get, well, that is not how wizards work in this game. The amount of spells they can cast is part of their class balance. The ability to summon a burst of power comes at a cost - if it didn't, then there'd be no reason to use a class that has a constant medium level of power when you can just be running at ultra power the whole time.
Part of the experience is to go beyond the single encounter challenge and play/strategize on a higher (or bigger, if you want to call it that instead) level. If anyone is still having a hard time of it on easy, I recommend reading some guides.
On a side note: Just because some other game's rules let you have unlimited rests in the wilderness does not mean that breaking the rules in this game is not cheating. Breaking the rules is, by definition, cheating.