Dinosaurs on a Spaceship - S7-E3
Revealing mistake: The Doctor tells everyone to run, which they do. As they go around a corner in the distance, the actors at the rear of the group, presumably believing themselves out of shot, slow to a trot. (00:05:04)
Chosen answer: 1) When Stephen Moffat took over he ignored a lot of what had been developed before (there is not in-universe answer). 2) It would have killed Rose, so the Doctor absorbed the energy. His body regenerated before the energy could do a significant amount of damage that would prevent regeneration.