So, if you can't do certain quests that need to be done to progress. Then how can you finish the game? The reason I bought these DLCs is too experience everything the game has to offer. Otherwise what good is it? They should have made it so merchants can be knocked out but can't be killed. They can be knocked out and robbed and so on, but never really die. I wish i knew this stuff before i wasted my money on the Dawnguard DLC. It's my own fault though. I should have asked more questions before hand. I had no idea they would come out with a DLC that hinders the game. Of course there are no refunds. How annoying!
I don't think they can kill anyone essential to major quests. Those NPCs are programmed as "essential" and cannot be killed.
But some of the non-essential favor/quest givers, trainers and potential followers/marriage candidates who help fill out the game--and give the immersion aspect of the game (one of Skyrim's selling points!) more variety and options--can be killed. And this is why I hesitate about getting Dawnguard, because I don't want that for
every character.
For example: Lami and Benor, both in Marthol, were killed in one dragon attack in my Redguard's game. Lami gives you a minor quest to find a book, and getting her book counts towards thaneship in marthol (and there's not many favors/quests you can do in that hold to begin with!). She is also one of the alchemy trainers available to you without joining the Dark Brotherhood or getting one fo the DLCs. Benor is a potential follower and marriage candidate, who can also be recruited into the Blades (in you choose to do the optional Rebuilding the Blades quest).
Now, imagine if you were playing a game where you had dragons AND vampires killing off potential gust/favor givers, trainers, marriage candidates and followers, even with characters you didn't want o do the Dawnguard quests with?
As I understand that you can, on Xbox, delete add-ons for games from your console's harddrive (and download them again later with the some Xbox profile you purchased them with--i don't now if this works with a bundle like yours). However, what if, like I am now, playing two different character concurrently, and only want to to do Dawnguard with one of those characters? Why do I have to put up with vampire attacks in the other character's game.
To top it off, there's all this cool stuff in Dawnguard that I'd like access to but sans the bleeping vampire attacks.
Yeah, the game designers didn't think this through.