Very true but even if Batman goes off towards the bomb, which is the most logical reaction, it would still come off as a gimmick to have Joker make a cameo to blow Bane anyway. Even if Joker was in a few scenes in the movie (let's pretend the story remains intact for the most part) it's still weird. Some interactions with Bane or making it about the fact that he doesn't agree with his mission, that helps the flow if he's shoots Bane in the head with a shotgun. But it's still like "OK he disappears like a ghost, but now Bruce aint gonna quit Batman cuz he still has Joker on the streets".
See i like how he's blown away like nothing. He gets what he deserves. To be blown away like nothing.
Sure there was impact! He took a canon to the chest and was thrown across the room like a ragdoll!