It looks nothing, I repeat nothing like the art for a Hearthstone card. Hearthstone cards don't use in-game models, especially a model that was created in Warlords of Draenor. That's just wrong. Its also not part of a trailer for Hearthstone because it looks nothing like the trailer art style they use. Its either fake or WoW related.
That's a Kul'Tiras solider and we've datamined Kul'Tiras questing sets in WoW. Saying its HS related at this point is just a fallacy.