I am having a lot of trouble opening my NAT on Black Ops 2 for PC.
I have followed the guides on portforward.com, Have a static IP and have all of the neccesary ports open, however in game NAT is still strict.
Here is proof of It being port forwarded and still strict: NAT broken? - Imgur
You might want to try another brand of Router. It could be your router performance issue. Try to borrow from someone if they have a spare.
Just make sure your firewall in the router isn't active.
It commonly known that games are poor in handling ports correctly.