Transpose main porpuse is so you dont have to cast twice to get Umbral Ice or Astral Fire back up. If you use Blizz or Fire they cancel each other out. So you use transpose to you always have full MP or Astral Fire up at all times. No MP hit transpose while astral fire active converts to umbral ice, cast spells, fill up MP bar transpose go back to nuking. Rinse and repeat. Blizzard does not take the place of transpose it is to make a faster transition of one to the other. Makes BLM the High DD that is suppose to be without having to rely on RDM, BRD, or kneeling(FFXI) to gain MP back.