Don't worry, I care a lot about it too.
To me, it's no surprise, because the lore/story/background of Warcraft is what drew me to Hearthstone in the first place. It actually got me back into WoW for Mists because of how much it played on those existing concepts. And I have no doubt that Garrosh, Thrall, and Gul'dan were chosen as heroes because of Warlords of Draenor co-existing at the same time.
What I appreciated about Hearthstone's approach to Warcraft-ness was how it set a new bar for the acceptable lore, characters, settings, etc. From the very beginning, we not only had Elves, Humans, Orcs, and Dwarves on cards, but also the likes of Draenei, Pandaren, Worgen, Ogres, and Blood Elves. No longer was Blizzard reaching back to the dry well of WarCraft III. They smartly chose to include all faces, places, and races. Even the original board themes -- Stormwind, Orgrimmar, STV, and Pandaria -- included the, at the time, fairly new Pandaren architecture.
All the different nostalgic locales and locals that, to me as a WoW player, tugged at those strings is the reason I keep coming back. The fact that Varian Wrynn is a Legendary while Anduin is the hero is probably the best example of what I'm talking about. The fact that Ironbeak Owl not simply "Owl" but Ironbeak Owl proves it, because that is a specific creature/mob in a specific place in the world of World of WarCraft. Stranglethorn Tiger; Cairne Bloodhoof and Baine Bloodhoof; Mekgineer Thermaplugg; Dark Cultist; Sylvannas Windrunner; Defender of Argus; Chillwind Yeti -- every single card let's you know that, hey, these aren't just cards for the sake of being cards, there's some history to them.
Now, they've expressed wanting to expand on the lore by coming up with their own original Hearthstone-bred concepts. It gives more freedom. We've seen this with League of Explorers, which is based on the WoW group in-game but clearly added original characters like Reno, Elise, and Sir Finley, while still having the classics like Brann Bronzebeard. So then... wouldn't it be cool if these original ideas then fed back into the core game? I think so. As we get further into Hearthstone's life, I have the sneaking suspicion they'll go further down their own path and simply use the WoW games as inspiration.