Fortress def, quick riposte 2, Ignis, and try giving him a Slaying Lance refined for defense. He will reach 45+ defense, hitting for 36 damage Ignis every encounter on enemy phase.
Agree on the build, however if you don’t like fortress defence (I don’t like the attack loss), defence +3 is a cheap alternative in the a slot (and seal too if you don’t want to use deflect melee or close defence)