Chipp, the artifacts are typical of polygon normals getting messed up. As you noticed , you can fix with brute force by thowing more polygons at it...making artifacts smaller and less visible, but the problem is still there And the hipoly count can be to much.

Other solution is to fix normals by hand in a 3d app. A rounded normal on the shader does this, but its a quick and dirty workaround.

With this example it is an easy fix although on a more complex model it is laborious.

The issue appears on trim edges and needs to be adressed by the exporter.