According to the latest 'Letter from the Producer', they aren't adding the Zodiac weapons in the next patch, BECAUSE not enough people have obtained Animus yet. So to those of you saying "Its supposed to take a long time", I don't think that argument is going to fly anymore, because it is taking long enough to collect that it is delaying patches.

... the release of these new quests has been postponed. Our reasoning for this decision is, in brief:
  • Many players still have yet to obtain an Animus weapon.
  • We would like to incorporate feedback regarding the difficulty of the Zodiac Weapon quests.
  • We are working to increase the number of locations where materials for the next upgrade can be obtained.
However, this also tells me they were intended to be more accessible then they currently are, and they might be altering it to increase drops to a far more reasonable rate (I assume on par with typical item farming).