You do understand that the different varieties of this bug appear to depend on partial completeion of a number of other quests potentially being at a certain state when you try to speak to Esbern, right? I'm not excusing the existance of this bug, just stating that there must be litterally THOUSANDS of different potential combinations of this quest and all the other game quest that would have need to been testing before the release for a QA test to have caught something like this. I have done this quest beyond this point a dozen times and seen NO issue, so your claim of NO QA AT ALL is just hype.
You do understand that the main quest is
100% linear (along with most of the rest of the game) and that there is nothing else that could influence it (apart from a couple NPC phrases towards the end, depending on who you side with in the civil war, and that's all). You do realise as well that it is so short that it ends before some other RPGs have even finished with their tutorials. And you do realise that the bug is simply an unpacked voice file, nothing to do with whether a game is small or big, linear or not, and thus will ALWAYS appear (at least in the pc version)
So, provided you do understand all these, I repeat: how can the QA miss THIS? I don't care if they miss the blood on ice bug or the fact that dragons sometimes are petrified in the air or other bugs in side quests - in fact, I do find many of them understandable, and the game is very much playable, since most of them are not exactly game breaking or anything. But Esbern - no, you either have at least one person play test the retail version for a few hours and see that at least the MAIN quest is working perfectly, or you just ship it as is and find out that half the main quest is bugged from the forums. Sorry, there is no middle ground, unless they were so pressed for time that they couldn't spend 1 morning to test the damn thing and 5 minutes to fix the most important bug in it...