No, I didn't say that. I was just trying to say that not everybody's results will be the same. It's impossible to effectively 100% test games like this, plain and simple, and someone will always run into bugs that an entire group of testers wouldn't run into.
No, but it IS possible to effectively test games more than 0%. And with the sheer number of people having RIDICULOUS problems (Of the people I personally know who have the game, only a couple are having worse issues than me right now, but many others are close), I cannot be thoroughly convinced that that happened. It's just so... broken. As to your question for "if it's been around for a long time then how does it relate to Dawnguard?", if the base game still has some pretty terrible bugs out there, like the Elemental Fury shout crippling dual wielders, then why are they releasing a whole swarm of new bugs? Until all the widespread bugs are fixed there shouldn't be a whole lot of other priority, and certainly not more things introduced that can destabilize the game, especially when the release in question itself is ridiculously unstable.
Yes, it was a miracle you were able to start it (I personally can't start it at all, or even continue with my regular save game because of Dawnguard).
What are the chances that someone else in the world has played the game in exactly the same way you have? Picked up the same items? Triggered the same quests? Completed the same quests? Triggered and completed quests in the same order? etc etc etc. Basically, your save game is very, very probably completely unique. Now the chances of someone during testing setting up the game in the exact same way you have, or the exact same way I have, are pretty much non-existent. Any combination of things you did to create the save you have could be responsible for the conflict with Dawnguard. Note, I'm not saying this is your fault, it's not, but you need to understand why things like this can and do make it through testing. Especially with a game as complex as this.
How many of the issues in this forum are happening to everyone? How many of them are happening to even a small majority?
It's not like all the dragons are flying backwards this time around.
My game is mostly unique, yes, though there aren't as many variables as you seem to think. Also, most bugs can be accomplished by either very general methods, so even if my game has been played in a very different way than your game, a decent amount of bugs that you're experiencing can easily be experienced by me as well, and most of the issues I'm having are being had by a decent number of other people as well, so it's not like I've discovered some highly unique bug, especially the one that's currently making the game very frustrating to play since it cripples my level 41 character in combat unless I can kill things with a bow before they ever get to me because other than One-Handed, no damage-dealing skill is above level 10 or so. I've played Arena, Daggerfall, Morrowind, Oblivion (unfortunately), and now Skyrim. I accept that every game Bethesda ever releases will be full of bugs for a certain period of time, but that doesn't mean they should be ignored or neglected as badly as they are.
Better release one before that, because it looks like quite a few people are having serious problems.
I do know a few people who aren't having major problems with it so far. Emphasis on the word few. Yes, it would seem that Dawnguard will be crumbling away for quite some time because I don't anticipate a lot of this stuff getting fixed very promptly, especially if vanilla Skyrim is anything to go by.