Aetherial Mimicry in general doesn't count towards spell slots, is simply an interface to become a Tank/Healer/DPS, available at level 1. You actually become that role too for the purposes of "role slots", and for things like tankbusters or boss autos.

Tank Mimicry causes Tank Augmented skills to become instant cast abilities.

Blue Mage gains a Limit Break based on which of the three Mimicry's it has, Tank LB, Healer LB, or Caster LB. A different DPS LB fix could simply be a free cast of Final Sting/Self Destruct without killing yourself and having increased damage under "Limit Break" Status or something.

Make Angel Whisper's Recast significantly reduced under Healer Mimicry.