I agree, I think tag team would be fun as hell but i'm pretty sure it was mentioned somewhere that there would be no tag-team. Don't quote me on that though

Unfortunately someone did post an article on another persons thread, who also asked about tag fighting, that tag fighting wont be in Injustice.

Sucks since I wanted to play as Nightwing and Arrow or something.

Im actually hoping in the future Injustice may release an update or addon that would enable Tag fighting. I can only hope so

You would think so? I would be willing to pay for the mode too not much but willing to. I mean like I said it would be different and make it alot more fun for this game