Disclaimer: I've never played any of the Warcraft games or WoW and have no familiarity with any of the lore. My entire experience of the series is the Leroy Jenkins video, the South Park parody and 2 minutes of watching my cousin pvp.
Having said that, man, that was a just a brutally awful excuse for a movie and I can only imagine knowing the lore and having expectations of it would make it even worse. They could have saved some money and let Uwe Boll make it and I'm not sure it would have been any worse. Of course it's still going to make a ton of money and spawn a long franchise, but ugh, just terrible.