I don't know what JDS can do to get better other than keep working his cardio. Technique wise the only thing I see helping him is working on timing a knee with a takedown attempt.
What sucks is just like a flash KO... we never really got to see this fight unfold. JDS was hurt beyond recovery and then gassed beyond believe after the first round. We have no idea how the rest of the fight would have played out. How long JDS could have kept that pace before tiring.
I think JDS needs to either work on punishing failed TD attempts or keeping his hands up and possibly sacrificing some of his TDD. He showed the ability to get back up despite his condition. He may want to take his chances going to the ground than taking a big shot trying to defend the take down.
I'm not sure you can ever be on Cain's level for cardio but it's worth a shot.