A player in the recent lan party stream said the attrition mechanics were grossly unrealistic. The response from the Paradox rep: people cry when realism is introduced into the game.
The bottom line is an important part of EU4 is letting people feel good about painting the map. It's not about playing a game of difficult strategy.
You won't see any change.
I have something to show here:
Do you see that attrition number? This was an extremely fast and successful war (3 years exactly), against about an evenly matched foe. This is Ottomans, so their provinces are prone to attrition losses… NOT. They're not. I fought also a bunch in Malaya, but a very small force was involved there. Most of the fighting took place in Europe. And as you see in the sidebar, I pay attention to that, painfully so in fact, only grouping army when needed. yet, in this 'attrition doesn't matter game, that makes up for 44% of my losses. 44%. While babysitting it, and fighting mostly in an area whose attrition is supposed to be fine (and it is, really). But yeah, 44%. I'd say attrition is already on the high end if you're having ~half losses due to attrition when fighting such wars and babysitting them.
If you want attrition, attrition is in the game, it works FINE. For the most part. Because in some areas it's out of control.
If you want uncapped attrition, I'm sorry but that got taken away from a reason. It's just way too easy to abuse attrition. Planting a bunch of forts in the desert isn't really my view of an extremely interesting strategy games. Also, it makes the game harder for new players AND easier for experienced players: Whether you teach AI-chan to work around it (splitting her forces > meaning you can pick them off that much more easily) or you don't (plan a fort in siberia and watch them go full lemmings on this), it's just too easy to abuse.