Plus in MKX, you have Johnny, Sonya, Cassie, Liu Kang, Jason, Goro, Jax, Kano, Kotal, Leatherface, etc.. whose powers/abilities could all be described as "punch stuff really hard and maybe throw some kind of energy" and they all play totally different so I don't buy any DC characters invalidating or replacing any. The difference between Deathstroke, Deadshot, and Red Hood is easily larger than any of those MK characters.
Like seriously describe Kano's abilites.. he.. uh.. throws knives... Jax can uh.. punch things.. and say one-liners... Kotal can also hit stuff real good