I finally got a replacement router from my ISP and now I have my 9ms ping times back, the full 120 meg download, 8 meg upload, and I have an open NAT. Now I cannot kill ANYTHING with a full clip. I have loads of assists though.
I highly recommend you switch to a wired adapter if you haven't already. Doing that will make a far bigger difference than changing your router or fussing with DMZ settings.
The wired connection adapter is actually slower on the Wii U than wireless now that it supports wireless N. I do have an adapter from my Wii and have used it occasionally with mixed results. Might give it a go again now the line isn't really dirty.
MUP-ANIMAL on Wii-U & PS3 KOFFING* - Member of the POKEMON Clan