There is concept art of Dairou in MKDA, as he was going to be in that game. He's a kinda medithisthingisdisabled Chinese looking swordsman, with old style armour. We've yet to see what he looks like in MKD, but I think it'll be something similar. Some people think that he's Hotaru, but I believe they are different, and it's been rumoured that Dairou will be a rival to Hotaru.

Ben is an American karate champ, besides that, we don't know anything about him. There have been pictures of this guy, and to me, Ben is the least impressive of the new intake this time. Just some average karate guy, who looks heavily based on Ken (SF) and Jin Kazama (Tekken).

I hope this helps you.