Sure, I'm making it a problem for me. D&D can feel a bit bloated sometimes with the sheer amount of everything (all the different planes of existence, all the different monsters, and so on and so forth).Why would overlapping ever be a problem? It has never been a problem, unless you make it so.
I think one of the reasons I like the Dragon Age setting so much is because of its simplicity.
You've got the natural world and the spiritual world, which is referred to as the Fade. It probably corresponds most closely to D&D's Ethereal Plane, but it is home to both good and evil spirits. The good spirits are all embodiments of virtues and concepts like justice, while the evil spirits are all representations of the standard sins like pride, rage, lust, etc. The Fade is interesting because it's where the minds of all living beings (except dwarves, strangely) go when they dream. It also appears to be the gateway to heaven. There's not really a hell, as such, but there is the equivalent of the Underdark, where goblinoid type creatures live. There are also creatures referred to as "archdemons" that manifest as massive dragons. There's more to it than that obviously, but I feel it really distills things down and makes it all a lot easier to remember. There aren't a million different types of fiend all from slightly different underworlds. All of the supernatural elements of the setting come from one place. (It makes me think of the Aang/Korra Avatar setting, which also has a natural world and a spirit world.)
And before anyone says it, yes, I own the three Dragon Age TTRPG box sets that Green Ronin put out some years ago. I just haven't ever had the chance to play/run it, as it's hard to find players willing to try something that isn't specifically D&D in this part of the world, so I've been making do by trying to incorporate ideas from Dragon Age into my D&D worlds.