I could be wrong as there is no way to test dps that I know of right now, but I personally use Transpose as part of my rotation. To me it just seems intuitive to spam fire then Transpose to get instant astral ice. Otherwise you would need to cast 2 ice spells to gain the mp regen. Also, I'm only level 24 right now, but my general rotation is basically fire spam until you can't, transpose, thunder, 1 to 2 blizzard which you can time just right to have your last mp regen tick as you are in the middle of casting your new fire spam. But let me know if I'm wrong on this, better to find out sooner rather than later.