BG doesn't have limited resting and have some decimating spells,yet it gives you a challenge. A good team rpg needs some op spells in later levels,the important thing is to be fun.
And that's why Mages were overpowered to the extreme, so much so that you were actively gimping yourself if you aren't playing a Mage. You have to consciously deviate to play another class. Sawyer's intentions are well-known, he wants Wizards to not be overpowered and each class to have merit, that doesn't preclude anyone from having "fun".
"balance" is even more meaningless buzzword.
No, it's not. Not only is it objectively measurable, it's the only way a class-based game can make sense. The IE games heavily slant towards Mages/Sorcerers, making the other classes merely footnotes to their gamebreaking natures and, by extension, fairly pointless.
Excuse me, but all of this stuff about resting being limited or unlimited. Isn't it basically the same argument that people on Something Awful made that led to creation of Empower in the first place? I'm pretty sure that Empower as a "per-rest resource" was left in the game precisely in order to cater to those people who played PoE1 as if resting was limited, even though in the big picture it really wasn't. So the intended audience for Empower wouldn't constantly micromanage it.
Who cares? It's ruining the combat now, better incise it before it starts to breed an infection.