Callihan did get a bit better in Impact, but more recently he's closer to NXT form than anything.
As for Darby... I dunno. I think him trying to climb the Everest or do dumb stunts outside the ring may be more dangerous to him than anything he does in his matches. Unless he starts hitting his head and getting concussed, which he's mostly avoided somehow, he's okay. Skateboraders can bump like no one's business.