According to wiki
Normal burst = AoE damage (~4000 damage). Applies a 3 turn debuff that freezes cooldown of all abilities. (Eg: If your ability have 3 turns left before it comes off cooldown, it will be stuck there frozen until the debuff wears off.)
Additional Note:
Rage burst = 3 hits, random (~6000 damage per hit)
If you have elemental advantage and around two stacks of ATK down debuffs, you can cut all of this damage to around 2000 for normal burst and 3000 per hit for rage.
How do you intend to deal with this?
She doesn't seem to be harder than Ragxion in my opinion.
My only problem with this is that unless you have SSR Thunder to outdamage it and kill it before it kills you, you will be stuck with a healer-less Thunder team unless you supplement with Andro or Joan. Discuss.
Regardless, I intend to use all black grimoires that I have this Advent and the next to MLB the SR Thunder Kamis.
This is the team I intend to use.