Maybe Spoilers. This text is my own opition.
1. Grommash has no nipplerings (1). At the Box Art he has.
2. Gul'dan says to Grommash "Everything" (2). Why isn´t Gul´dan lying, and saying (for example) "Nothing"? I mean, Gul'dan wants that Grommash drinks the blood of Mannoroth.
3. Why isn´t Gul´dan helping Mannoroth to defeat Grommash and his army? Tom Chilton said in a previous interview that the final raid will be influenced by the Burning Legion. And Gul´dan is working with the Burning Legion, and Mannoroth is working for them too, so why Gul´dan isn´t helping Mannoroth? I mean he is a very strong warlock and he just let Mannoroth die and his plans die with Mannoroth.
4. Why Mannoroth didn´t see the Iron Horde army? I mean, the army was in front of Mannoroth, same with the Iron Star (3). Why Mannoroth didnt escape? Is he so dumb that he is meaning that he can easily defeat this big army?
5. Grommash looks to the left side, but he cant see Garrosh (4). Garrosh is noding and looking at Grommash. This makes no sence, why should Garrosh noding to Grommash but Garrosh know that Grommash isn´t seeing that?
(1) 3:37
(2) 1:06
(3) 1:59
(4) 0:50