Is big bang gonna fix Hp?

It was never broken. But to sort of answer your question, every job gets a 20%; increase to HP. But 400 HP to 4000 HP isn't much.

The fact that classes had to pay loads of actual money to fight certain bosses at a decent level or at all means that the system was broken. But as for the increase in HP, is that just level-up HP or just the HP-increasing skill, 'cause if it's the latter then not all classes get that (Corsairs ;_.