So the 13631 HBP is actually reachable for me (Ilvl: 545).
I reforged/regemmed and even changed 2 enchants to reach it.
These are the stats i actually LOST:
Mana regen: 1621
Combat regen: 810
Crit chance: 396
Mastery: 8019 – (16.71%)
I haven't actually tested it in a proper 10M environment, but what i've read is that benefits you gain from the HBP make up for the mastery loss.
Anyone with some experience that can tell me more about it?