Burn teams will definitely be significantly more powerful with this unit. It's interesting how it has more than one trigger for the awakening of the EGO, being at +45 SP or losing two teammates as
@wtfNeedSignUp speculated.
I forsee Faust being a necessary unit in the team compositions including PhilipClair since 2 of her EGOs heal SP, she's also the only one that has a passive that is able to heal SP (Kromer Faust and butler Faust come to mind) potentially extending the use of his EGO and I'm not counting Middle-Meursaults assist since his SP healing requieres 2 IDs from the same faction.
Another big change for teams will be Rodya's scarlet desire EGO. Units, more specifically bosses, not loosing bleed count is already massive and it also gains buffs from the bleed. If Rodya gains a better bleed ID (That isn't her KK one) then it could definitely benefit more from the EGO passive.