There's a lot of wrong information there.
The song (studio recording) is not in Em, but in F#m - except for the intro, which is in Em. Death on the Road version is transposed to Em, and to play it that way they did not tune down the guitars, but rather modify the intro, which is now in Dm. They took the interlude part from before the solo and inserted it as the new intro, but a step down from the rest of the song. (The change to the intro happened already with Blaze, I don't think they ever played the album version of the song live.)
They are most definitely playing in E Standard tuning. As for why they transposed it, I'm glad they played it and were wise enough to let Bruce do something new with it - if "Man on the Edge" on The Wicker Man single B-side tells us anything, it's that Bruce can hardly sing with the same power as Blaze do in his strong registers. The rule is that the key is always changed to fit the singer, and for once they were able/willing to do so. The added guitar (Adrian) is modification of Dave's part on the album version, one octave higher. They do modifications of older songs all the time, so it's hardly something new.
As for the timing-aspects, it is one of the reasons why I like the Death on the Road version more. The tempo is interpreted quite freely, with tempo changes between sections (most notably intro to verse change) and after going up, it goes down again after the chorus. It just flows so much better than the rather stiff album version. So what if there's a moment when someone isn't in sync, the song hardly falls over. Again, nothing new concerning the band.
Janick's playing is certainly messy, but I'm not distracted by the timing problems or the out-of-tune bends in the solo. It's such an energetic performance that it far outdoes anything else on the DVD in sheer excitement. To me, that's what Iron Maiden is about.
