I respect your opinions, but I disagree. I don't care if you like Warcraft, play Warcraft, have played Warcraft or whatever, but almost any gamer worth his salt knows who Thrall is. Everyone knows who Diablo is. It's not just the physical appearance either; they're well-established characters with well-established backstories.
I, personally, love the Diablo and Warcraft lore, so I get excited about new expansions because of the new roads for our characters to take. I don't see an ending to ANY Blizzard game. Instead, I see just another locked door waiting to be opened.
I wish this game actually felt like a sequel to Diablo II instead of its own thing. I just feel like Jay wanted a "clean slate" after the fallout of Blizzard North's collapse. It's a slap in the face to all of the fans and I still have bad blood about it. I know it's their game, but Blizzard lore is legendary in itself.
Anyway, I am hoping the next expansion (i.e. after Reaper) will give us the ability to respec into different fighting modes or something. Maybe the Demon Hunter could become a melee Assassin? Maybe the Monk could exchange some of his melee abilities for mind-based ranged attacks? Maybe the Barbarian could be more Spartan (e.g. spear/ranged attacks with shield and limited melee)? Perhaps the wizard could buff others with arcane magic, or have the ability to wear magical armor to defend herself in melee range (e.g. Arcane Warrior in Dragon Age)? Just an idea.