The first one caused a drop of ~70 USD on its announcement (~2014-06-11) which was reversed when it was known that one bidder had bought all the coins (~2014-06-30).
The ssecond one (announced ~2014-11-17, result known ~2014-12-09) did not have any clear effect although there was a ~25 USD drop on the day before the result became known (a leak perhaps?).
Auctions are good, rich dumb guys buy all the btc, they hold it, less coins in circulation, btc bagholders win long run.
It depends... Those coins are now out of the active market, whether open (exchanges) and OTC (off-exchanges). The auction will take a lot of dollars out of the pockets of people who would otherwise buy bitcoins in the market; so it will put a negative pressure on the price.
If the coins are bought by long-term hoders, the effect will not be immediate; simply there will be less money around in the following onths. If the winners are short-term speculators, the drop may be immediate as they offer the coins for sale.
(On the other hand, perhaps there are people who are not buying BTC now because they hope to get a better deal at the auction. If they do not win the auction, perhaps they will start buying from the market.)
... wrong, this a "Buy the news" moment, because all the psychology that you meticulously detail here with great effort has already been priced in awaiting this announcement. Only a few slow beartards traders will get caught expecting any drop ... that's all folks, next stop 2 fitty.