It was pretty long, actually. The burning crusade's intro was less than 3 minutes (around 2:50.) and the first video was slightly longer than 3 minutes (because of the long "ten years for Warcraft" which last for almost 25 seconds!!!) but still shorter than this one. This
is one of the longest cinematics blizzard has ever created. But more importantly, it was by far better than the last two. There is enough action within the game; the intro is for presenting the story in my openion. I, for one, was happy to see another cinematic which focused on that, just like ROC and TFT intro cinematics.
Besides: I am tired of the cinematics in the style of "characters fighting other characters and doing stuff" it is boring and a bit lame.