So Transpose just seems like a filler for levelling until you get Blizzard 3 or Fire 3? Fire 3 does the same job with moderate damage, Blizzard 3 does it as well with some damage and faster regen.

I'm surprised because it seemed like a core class ability but then just got worked around by the damage spells. Any reason to still use it?

I can only see some where you're in fire 3 and the boss jumped away and you want to go back to full mana before they get back. No enemy to attack might be where it shines. Not exactly as core as I thought it'd be.