U use wifi for injustice and wondered why it's bad??
I have no choice in the apartment I'm living in, I would play wired if I could. Injustice netcode is an improvement over MK9 but it's still not that good, it's not because I'm on Wifi. I've played on hard wired connections my entire life until I moved into this place and all fighting games I play with good netcode play the same as now. I'm on verizon fios, my upload is like 15mb and download is at like 30 (not that it even matters in fighting games). I will say Injustice runs really well with other players in the NE. I don't think I'm getting more lag than other players, it's just that some people tolerate it a lot better than others. If I had problems in all fighting games then I would say you are correct but my problems are only with the input lag in NRS games.
Delay has more to do with distance and the way the game handles the lag. A wireless router would be responsible for things like lag spikes and ect if the signal is no good. Even on a hard wired connection you can get lag from other users on the network. Wired is better but the Wifi is only bad if you get lag spikes all the time, that's not the problem I'm having.
We have played online before in MK9 and from what I remember the connection was great by MK9 standards. I was on the same connection then as the one I'm on now.
I have 0 issues in Killer Instinct, any GGPO netcode game and even games like SF4 and SFXT. I'm super anal when it comes to how well my fighting games run online. If my connection was a problem I wouldn't even play.