IIRC, some point during one of the betas, Yoshi-p said something about people requesting a job with haste and how he said we would never see it as a player skill because it would be impossible to balance it with the implemented battle system. If the effect is too weak, no one would use it (like Tri-disaster). If the effect was too strong, mobs would have to be adjusted to compensate (and that class/job would have a guaranteed spot in every party because of it).