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CEO, BS Comics
Oh, I don't doubt that character without abilities such as Mr Sinister's couldn't heal from completely physiological neuronal death - there's been a lengthy thread trying to get across that Wolverine cannot recover from decapitation. However Hulk wasn't dead as Cable first thought.
Whether or not his mind was slipping away is questionable. This is based entirely on an inference into the motives for Cable's behaviour - which really can't be determined. It's just as possible that Cable's urgency was due to him seeing a limited window of opportunity to free the Hulk from Onslaught.
However when he does enter the mind he doesn't enter to seek out the mind - as he resumes from where he was before when he entered Hulk's mind - or to reconnect any severed connections, or to prevent any links from being broken, he does so to free Hulk of Onslaught's influence. That is all that is shown - that Banner's mind was trapped by Onslaught's influence.
If the heart had suffered asystole then the lightning bolt did nothing, if it was an arrhythmia then Storm's lightning bolt defibrillated him - in which case, again considering his regenerative capabilities, he could have recovered from anyway.
Besides this massive aside that has totally derailed the thread, the real bottom line is Storm can't replicate such an incident alone.