I hope they do away with HP based on class and role. Classes and roles could and probably should affect HP in the way of giving access options to boosts, but should not affect the base number.
Classes that are Defenders should for example get options to more uses and more frequent uses of Second Wind and more upgrade to HP (as per Toughness). Other classes may get these as well, but would only be able to take the basic boosts.
More uses of Second Wind effectively translates to more HP in the end.
I think HP should be based on race and character level.
Dwarfs: Sturdy so higher HP.
Human: About average.
Eladrin: Fragile, so less HP.
And so on for other races.