Well, if that's how Poser handles Ngons in the year 2015, then that's pure rubbish, mate.  They need better algorithms there, because that's just an aweful conversion compared to how it looked in Wings.  Try importing that same model into Blender, C4D, Maya, or any REAL 3d software, and  I bet it renders just fine.  I'm standing by my original statements. It's obviously POSER that is the problem, not the geometry.