I've assumed that this last weekend was (like past weekends) an older build meant primarily for stress testing, and that the many quest problems were related to problems with the phasing code. It doesn't seem likely that this many individual quests would be bugged, it's more likely a single phasing problem affecting many different quests, so I'm hopeful that all of this will be ready in the release candidate.
But this is a pretty big assumption. If it still fails as often in release as it did this last weekend, we will hang in there, but the game will be massively trashed in the media and word of mouth and the launch may damage the game permanently.
It would sure be nice to hear from the devs in the way that Path of Exile developers kept us all informed.
Whatever happens, good luck, and see you all on the other side!