Take the BG1 kobalds vs the POE1 Xaurip. In BG1 the kobalds were a real challenge at level 1 but by the end of the game you could eliminate a horde of kobalds in a few rounds. A fireball, few arrows you've defeated enemies you once ran away from. In PoE1 the xaurips on the beach were a real challenge and later when you meet the xaurips guarding the drake . . . they turn out to be even greater challenge. For lovers of balance that just good design -- both encounters had equivalent challenge ratings. But I felt robbed -- I never felt the satisfaction of feeling stronger because my toons had leveled up.
I feel this is a bit different subject though, not related to balance. It's having a wide enough enemy roster to fill all the player levels with unique opponents. PoEs reuses Xaurips and such multiple times because they lack monsters to pit players against. I think that is a problem, but not necessary related to PoEs "balance obsessions". If for example, in BG we would keep fighting goblins in stead of hobgoblins that would be bad - unchallenging and boring. PoE chooses to reuse Xaurip assets and create "different Xaurips". Its unfortunate, but something I am willing to forgive. I was however suggesting myslelf if PoEs would be better if there were less gain in power - that oddly came from my suggestion that PoE is not being balanced enough with too much powercreep if one is a completionist. And yes, a big advantage of having enemy types stay constant in power, is that they become a clear indication of how far players have progressed. That effect is greatly dimished if, like you said, same enemies grow with us.
For apostles of balance, players should never be confronted with encounters that don't challenge them. The rule of cool says sometimes absurdly imbalanced encounters are fun.
I mean it depends, if that encounter was meant to be challenging - what's the story of this encounter. In the same vain the game should present it's content with a coherent way - it's fine to run into too hard encounters, but if it's becomes too frequent and without perceivable logic behind it or is not properly communicated (cough Kingmaker cough) it becomes unengaging as well.
In the end it comes down to creating enjoyable content and story, and if player's possible power level can vary too greatly (and not due to roleplaying nor story reasons) then that becomes a problem.
