Sorry I haven't been able to get back to this, but this has become a constant problem now and is happening on every mesh I bring into Substance Painter, which makes me think it has something to do with my export settings from Maya.
Here is an image of this hard UV seam problem happening on another mesh:

Here is .fbx file of said mesh:
https://drive.google.com/open?id=0B47cFWX2cub7bzBQS181Y0d4ZW8I've tried softening all normals in Maya, that didn't work. Or I didn't do it right. Either way, it seems like the UV edges are getting hardened, but I can't seem to figure out how to stop that from happening.
I'm exporting out the .fbx's with the following settings from Maya:

Literally everything else in the .fbx is turned off. And the .fbx year is set to 2013.
Edit:

Okay so I should have inspected the channels before assuming it was the mesh, and it looks like the Curvature map is the culprit for these seams. If that's the case, how do I rectify the curvature map?
Edit Edit:


Okay so switching the baking to perVertex instead of PerPixel and disabling seams seemed to create a much better result
for the Curvature map. f&*k!
Nevermind, this didn't fix the seams still showing up in the final material view. Which is weird, because the other maps seemed okay (seamed, seemed...okay, I'll see myself out).
If there are any other tips to creating seamless textures, I'd be all ears.