I've read that thread on NB and my experience completely disagrees with it. I've done a vorlauf on every one of my 404 batches and it has caused no problems.
As to rehydration, I know it's the best thing to do but I never do it any more. I've had no problems from not rehydrationg.
I can't comment on the dry yeast issues since I very rarely use it (FWIW, in the very rare instances I do
use it , I don't rehydrate, and it works just fine)
As far as volauf goes, I never
skip that step and have always done it since I switched to all grain 21 years ago. I want clear wort going into the kettle, and the vorlauf is the way to achieve that. I don't put any stock in in the hot side aeration issue mentioned in the page that was linked in the original post. I'm not saying the guy's science is necessarily incorrect, it's just not the issue he's making it out to be.
I mean, jeez...The hands down best
German style lager I EVER tasted (from a pioneering NJ micro in the early/mid 1980's) was made on a practically 19th century styled system whose wort chiller consisted of cascading the hot wort over a radiator like cooler. If THAT didn't create aeration issues, then I doubt sincerely that doing a vorlauf is going to cause a problem (especially since the wort is then boiled afterwards). The beers they made were incredible (Unfortunately, as is often the case, they were a bit ahead of their time and folded in the early 90's after at least one management/ownership change).
The whole HSA thing is overblown. I'm not saying that it doesn't have detrimental effect in some circumstances, but as far as vorlauf goes it's definitely "relax don't worry" thing... doing a vorlauf is not going to harm your beer and it will more than likely help