“In this case, however, China had nothing to do with it. Lead mission designer Dave Kosak told us that after reviewing the full Hearthstone set, Blizzard decided that the art on some of the cards simply didn’t meet its standards, and that Blizzard “wouldn’t print those same cards today.” PCGamer says.
Source: N4G PC Blizzard says Hearthstone card art changes have nothing to do with China