I just ran into a majestic hart near an orc camp that said 'This creature cannot be tamed.' on my first try. I fended off a few orcs and tried again. It was suddenly tamable. The orcs weren't attacking the hart and it's clearly not part of a champ spawn so I figured I'd report this. I heard someone else in IRC have a similar issue so it may be worth investigating. This occurred near (1049, 1328, 0) in game.