This is an older thread, but I'll go for it anyway, since this is something I was thinking about.
WoWTCG itself has tons and TONS of heroes at this point. I think I have almost a full epic collection box of hero cards at this point.
I'd like to see Hearthstone have more hero cards, even if they are EXTREMELY rare and for money. Because, honestly, I already clunk a fair portion of my budget on WoWTCG, so for me this is just taking up that spot financially (and allows me to retire my cards, etc).
I WOULD like to see loot cards added, since it seems like Crytozonic has kind of done a poor job to date with adding a Monk deck and releasing the newest epic collection to America. Plus, it'll get more people paying for cards. I still intend to get IRL tcg cards now and then - there's something nice about it - but I can see this VERY quickly taking up that spot, especially once it reaches live.
I kind of dislike that most of the heroes are orcs - IRL decks, I can have a mage that's either Azshara or Jaina, for example, or a warrior that is a Troll or Garrosh or an orc, or some kind of human (I admit I don't pay as much attention to my alliance cards). I love my Garona Halforc rogue, too.
I know it's nto exactly WoWTCG, but it'd also be nice to have heroes of the same class with slightly different abilities - at least for flavor. I guess some can kind of be OP, like Illidan with his minion summoning (I have a few TCG cards that are similar, though).