For the person who asked if they should play the DLC during the main campaign or after ...
You can start it any time after you get to Skyhold and from what I hear the enemies level up with you. But I've also heard you will get to certain portions in the DLC where it might be too difficult to carry on, the game's hint that you should leave for a bit and come back a couple of levels later.
There's no benefit to completing it before or after the main campaign. I played it with a character that has already completed the main game and maybe got one story related battle cry dialog in reference to that fact. Something along the lines of "I did not defeat Corypheus just to fight these guys in the end."
The first half of the DLC felt a lot easier to me than the second half. There are two enemy factions you will face and the faction in the second half are far more difficult because of their sniping abilities. Similar to the archers in Jaws of Hakkon.
Hope that helps. 
ETA: There's a vendor you get pretty much right at the beginning of the DLC that buys back all of your gear at outrageously outlandish prices. I probably only had about 20,000 gold going into the DLC and walked out with 400,000+. So starting the DLC as soon as you get to Skyhold could be beneficial just for that fact, as it will make it a lot easier to buy higher leveled gear early on in the game.