Yes, that's what I was referencing to. After all if Irene was able to fool the mighty Sherlock, then it would make sense for John to have a certain paranoia concerning people really being dead, especially considering the circumstances of Sherlock's demise.

I can't imagine it making any sense at all for John unless of course Mycroft found out and told him what happened on the roof and made Sherlock jump. Would still not make sense though... why would Sherlock claim to be a fake still? Moriarty wanted to make him jump, for his friends, not proclaim to his friends that he's a fake.

I'm pretty sure John would have similar thoughts, therefore the "Don't be dead", but as you said he can't be sure and that spark of hope can be a very cruel thing.