To me it looks like those border edges are treated as hard by default, or the cage goes over the edge. Does it display some artifacts on the mesh itself? If that is a problem, I'd personally extrude one more loop from those for baking purposes only, and remove it once everything is baked properly. It's generally a bad idea…
Ouija, I tried filling in the eyesockets with some tris and that did indeed help. Is previewing in Maya sufficient for reviewing normal maps? or is there a superior option? here's the result so far: better than I expected, actually. but still issues where the fingers have borders with the palms: how are these seams…