I don't think that leveling up should increase your HP at all.
I think endurance will still count as a hp gain on top of the natural hp gain per level. In past games I always kept endurance low as gaining enough HP's to survive anything never seemed to be a problem. I'm looking forward to seeing how hp's affect gameplay this time around..
I hope the math is Initial level=80 + (Endurance x 5) + (Level x 2.5) = Max HP