In Odyssey and Torment, blue is notoriously good at putting cards into the graveyard, which explains why it has so few threshold cards (It would have an unfair advantage over the other colors.).
The only threshold card blue had in Odyssey was the feeble Aboshan's Desire. In the sets original design, however, blue had more threshold cards, but they were balanced out by having drawbacks when threshold was reached! As an example:
Testing showed that having blue fight itself with the graveyard filling cards and the drawback-threshold cards was a bad idea, so the Flock and its ilk were retired.