If the writers can actually capture the true menace and threat the danger to the two different universes share, then I can see plenty of reasons why DC should allow the characters to be brutal in ending their foes and as a DC fan expect to see. Here you have guys who hold to a certain ldeal that doesn't allow them to kill, facing foes who fight with a totally different mindset than what they have been expoused to. Guys were many are on a razor's edge between being either a hero or villian like Scorpion, where the villians are just way beyond anything in savergy than what they are use too, and where even the "good" guys are just brutal as hell in how they end conflicts, like Raidens total destruction of cilvilizations.

As a DC fan and a MK fan, I want to see how the DC heroes respond to this type of situation, where nothing short of totally breaking their opponent will suffice, because they know that their opponents are more lethel than most, and any thing short of that will see them dead instead. This would both enhance the element of danger we believe Batman, Superman, etc are in, and at the same time enhance the backstory of the MK characters and make them seem vastly more formidable going forward from this game into other installments in the series. It was also add a severity to the situation at hand in the game's story, that fore going Fatalities could diminish.

I think DC needs to allow the heroes to be totally brutal in how they end fights but within character, Superman stopping just short of killing but showing that the opponent is utterly finished, and enhancing the savegery of guys like the Joker, no reason he cannot kill. If the story is done right I would expect to see Supes destroying his opponent without killing them, or in turn being killed by Scorpion, and if done right as a fan of both I would see no reason to be bothered by this. This is a chance for Midway to strengthen its MK brand, and for DC to add an Edge to its characters, be nice if they allowed this too happen.