This can be achieved on dream battle 15 (Quick Mix). Dream battles are unlocked after completing the story.
I would recommend NOT using the armiger. This is because the time to perform this is wasted time. 1 minute is not long.
Go straight to the flans and build up a combo. Start using the support (I would recommend all). Aim for the skeletons first following this and use magic going forward on the flans. Remember to use magic that is not the colour of the flans. Roll to avoid getting hit. I got this on my first try with 59 seconds following getting an A+ and optional objective complete.
I have a video of me completing this achievement here:
Sorry, this Game Clip has been removed