I dont know if anyone has said this already but they should of made it where only allies or nobody can see where you ult'ed so that way enemies cant knife/ hold your body. Like yeah you can ask an ally to cover but I feel this will buff phoenix :)
A lot of times, you can just figure out where the body came from. Like if you heard the ult voiceline and 2 seconds later you see phoenix pop out of an angle to peek you, ofc he ulted in that spot.
Your knife holder will just have to go to that general direction. Yes knifing is only possible if you hold exactly besides the ult but you can still kill the phoenix by just keeping your gun out.