Orphan vs. Heat:
Okay. Above 40% HP Orphan has serious problems with Heat. Vile Exploitation followed by a Laser Orb will do some damage that sticks, but it's very low... 6% to Vritra at base. And Vile Exploitation only 2HKOs the hands... at base, which means Vritra will immediately stat down to make it a 3HKO. Orphan can throw debuffs in there but still unlikely that it'll take less than 3 turns of chipping to do 6% of Heat's health. Heat, meanwhile, in those three turns, does Regenerate/Inferno, then two turns of Agidyne x2/Attack x2, which removes 29% of Orphan's HP (factoring in damage halving to all but Inferno Howl). Slightly less the first turn due to throwing a turn on Makanda I guess, but yeah that's a 4HKO.
Towards the end of the fight Orphan gets Dies Irae, which is certainly MUCH better. It one-rounds the tentacles at base, so Vritra responds every turn with Inferno + Regenerate, which still manages 10%. So yeah, Vritra is helped enormously by having a damage source which is neither physical nor magical, but takes this pretty clearly.