I wouldn't trust anyone who gave Shivering Isles a 7/10. That was possibly the best expansion/DLC I've ever played, and IMO it was certainly better than vanilla Oblivion as a stand-alone product.
Be careful when you say that, it is your gaming point of view, these guys are testing videogames everydays. Dawnguard is like fallout 2, could have been epic but is "just" good ( neutral point of view ). You say dawnguard is epic but its just because you're a fan dude, and that's a good thing for you .
In the other way dawnguard you must admit is very linear and don't add anything new to the game (quests are just the same whatever you choose), except the fact you can be a vampire lord you dont have any impact on skyrim and people still dont give a .. like when you killed alduin. That was one of the main immersion problem in that game and they did exactly the same thing with dawnguard.
The problem is that when you watch the trailer you directly think "great at least we are free to be evil to eradicate the sun forever". Instead of that your imagination start to work and you think that bethesda finally understood all these complains... but you buy dawnguard and welcome back in the reality.
Im not saying DG is a bad dlc im just saying that i totally agree with eurogamer to stay on the thread, DG is not an epic DLC.