I think that this is completely a matter of groupthink. You have a bunch of people beating their chests about how good they are and how easy the game is. And this is the current shiny object that is trotted out as an excuse. If this was slashed I *guarantee you* that it will take less than a day for the same people to be back here complaining about the same thing with a different target. There's just no end to it.
The basic reason is simple: this is an open world game (which allows you to control what level you do things at). You can take advantage of terrain, which is a huge edge. And you have both a ton of "burst" capacity in the form of per rest spells /abilities and health vs/ endurance - remember that in BG every "unconscious" player would be a dead player. You can also create imbalanced parties and characters, which is basically impossible to avoid in a complex game like this. And you can withdraw and rest (no respawning monsters). None of these things are impacted, at all, by experience gain.
The bottom line is that experienced players will always be able to trivialize normal encounters; if you want more dificulty the only place to get it is in boss encounters where you can balance them around the players throwing everything at the wall and you can control terrain.
Any "fix" should be restricted to the highest difficulty level (and possibily target bounties, which really do seem to have too rich of an exp reward for their level. Conversely, I'd pump up the gold rewards - as, after all, they are bounties, and the fights are tough. And, no, you can't buy "every magic item in the game", or even close to it, with the cash available!)