Sooooo, from what little I have pieced together on the Internet, it sounds like the PC version wasn't ported by Rocksteady themselves- presumably they were focusing on the console versions- but instead got passed on to some other developer. Similarly, accounts suggest that the console versions are actually really solid, perform as well as can be expected on the hardware, etc. Hell, I think Digital Foundry called the PS4 version a 'tour de force' or something, so the actual base game doesn't seem to be shit so much as the porting job that this external studio did in bringing it to PC. Something that, BARE minimum, you'd think Warner Brothers or Rocksteady (whoever this external studio was reporting to) would have noticed before launch, even if just before.
Which brings me to the question... why the hell didn't they delay the PC version?!