After taking a quick look through the game files, it looks like DOCK chunks are a feature of the ship files, not the mesh files. I have no idea what DOCK chunks do or how they work, and Wing Blender was designed to export mesh files.
As for the performance boost, I don't think it has anything to do with OpenGL. After I get the mesh data from the mesh file, I have to construct a mesh for Blender, and it's the construction phase which was taking the most time. The loop on lines 297-305 of import_iff.py became much faster once I started using a dict, with the edges converted to frozensets as keys, and the edges' indices as values. I received another significant speedup once I moved the "bl_mesh.loops.add" line above the second loop that iterates over the face data. ("loops" are corners of a face, consisting of an edge and a vertex)