1. Kain does not perform a gesture to teleport, he fades out in less than a second and re-apears, you were probably thinking of dimentional teleportation which Kain seems to have to move the reaver slightly, although that I would say is gameplay.
2. All the Blood omen spells take about the same to cast, about a second, maybe less, its unimportant anyway, Safer has no feats in most areas so Kain could prob do him in with one reaver slash.