It is good news about heirloom improvement but 2h weapons have a big disadvantage - their bonuses are the same as one hand item.
For example champion - we have very nice 2h sword with extra ATK and base ATK ~800 at 6* http://prntscr.com/hddeed but bonuses of one hand + off hand are making that benefit useless.
Please take a look into this issue and make bonuses x2 for 2h weapons.
