Ok I'm going to bend the rules just a bit. So forgive me, but I intend to speak my mind. I voted yes. I'll list my characters first and then explain why I voted yes.
Mains: Zatanna and Nightwing
Vs Martian: Mostly Nightwing, but sometimes I will play Zatanna just to prove a point (a supposed 6-4)
Why I voted yes:
The character isn't BROKEN. A broken character is defined as a character who breaks the meta of the game by performing abilities that totally defeat the entirety of the cast. Kabal is broken, why you may ask? Do I even have to say? He has an ANSWER TO EEEEVVVERRRYTHING and defeats EVERYONE with NO even match ups. That is broken and EVEN STILL, he could be beaten. I believe the general consensus will define "fair" as "an equal ability for each character to have a chance at winning", if this is the case.. no character in any game is fair. Mostly EVERY character in EVERY game has good match ups and bad match ups. Some characters more than others, but thats just how video games are, especially fighting games.
Everyone wants Injustice to be this godsend of balance and fairness, where every character is viable in their own right and there isn't a dominant character ruling EVERYTHING. If this was the case, we have that game. EVERY character is viable in their own sense, it just happens we have a character who is better than most. This is a staple in fighting games. There are low tier characters people can play so they can try their asses off to be "different", you have a majority of mid tier characters that are all decent at doing their job and are mostly the bulk of every fighting game. And then you have the top tier characters who normally dominate a game and set a standard for other characters to defeat. If we dont have this, if we don't have "tiers" we dont have balance. If every character is just fucking amazing.. where is the balance? Its a hard concept to grasp, but hopefully someone will understand.
Anyway, thats why I voted yes, because if there isn't one character everyone has to fight to defeat, we don't have balance, simple as that.