If you are a developer, and you release a patch and suddenly, multiple people are having Audio, or Video issues, then it is most likely something you put in that patch. Especially if they tell you it worked fine the previous day.
My common sense tells me that Blizzard probably do too. The question to me is whether they listened to these people at all? Yes! Were they right to tell people (even multiple people) to check things their ends? Yes! Will they do so again if a similar problem presents itself? I damn well hope so!
The staff who man the forums can't instantly update you with real-time progress, in fact they're unlikely to respond to you at all for a bug report unless they require further information or the devs decide they should make an announcement.. which... they did, took a few days but it happened.
They made a mistake, they fixed it, alot of people seem unnecessarily sore because they were asked to check things their ends when it turned out it wasn't their problem!
Investigation is the key, from both ends, a developer may have caused an issue by changing something, doesn't mean they were wrong to ask you to check your drivers while they do the investigate it.
Couple of patches ago there were graphical changes, in the patch notes they pointed out that in-game graphic settings would be changed back to default - I'm certain when some people logged back in after that patch they thought "God, this looks crap" and probably ended running off to the forum to moan without bother to checking much.. and the biggest problem I can see with this kind of things is simple.. go look at the amount of people who have posted on quests saying this or that has been updated since 2.4 when it really hasn't they just didn't either notice it was like that all along or was changed earlier. People don't always give accurate and full information you have to wait til you see a larger than normal amount of reports of a type of problem til you investigate it fully - even after a patch. Until then you're stuck with then asking you to investigate.
Yes, in this case Blizzard made an error which caused a few people problem enough to bother reporting it, they fixed it - fairly quickly, along the way they asked you to check things out yourself, so what?
Edit: And what Ialaman said goes to the heart of it better than my own diatribe.. rate up for you :)