As for it being breath damage... I don't know. I've seen shell getting dispelled and then they'll take more damage from it. Which would make it magic damage and not breathe damage... because MDT doesn't affect breath damage.
So I don't think it's breath damage.
This obviously isn't a proof of whether it's breath dmg or not, but having a quick look at jp wiki it seems to agree that it's breath dmg:
(source)
Quote:
アロガンズインカーネイト
対象中心範囲
ブレスダメージ
ダメージは残HP量に比例。
ダメージキャップは2500超(TP100~199?)。
ダメージ分散率2人80%、3人75%。
Arrogance Incarnate
Target centred AE
Breath Dmg
Damage is proportional to hp
Damage cap is higher than 2.5k(?)
Damage is shared amongst people - 2 people 80%, 3 people 75%
I think both Aegis and Ochain are surviving because neither manages to kill you due to EA/Scherzo/Both. Best way is to just get a pld out there to test it really.
With aegis having a lower block rate, that means dom. slash could also potentially silence you more often? Along with the stun getting less likely to be blocked as well, unless someone can guarantee that A.I is magic dmg it sounds to me aegis just adds more complications.