You see, this is what I don't like at all. I think that's pretty close the level scaling.
I agree. I don't think the control-argument is good either. But there's no reason a developer can't "level-scale" in this way by controlling combat XP just as he could with Quest XP. That's the whole point. The systems are not qualitatively different on this point. Both systems can be designed poorly and well in this way. However Combat XP incentivize players to solve their problems via combat, while Quest XP leaves the decision up to the player. That is the single, most important qualitative importance and IMO the only reason worthy of debate. On all other points mentioned in the XP debate, both Combat XP and Quest XP can be used for the same purposes. On those points it is merely a question of scale.
The one part where I accept the Combat XP argument is if you want to play the IE-games like I did when I was a child. Just go amok and kill everyone like you were playing Grand Theft Auto or something. I don't believe that's a niche that Sawyer and Obsidian has any real reason to cater to however. Yet you can still do this in PoE, you just don't get rewarded with progression rewards for doing it.
(plus, in lategame IE, the vast majority of your XP comes from Quest XP or path-critical kills anyway)