Hey Xanax, I don't wanna sound offensive but what you describe is common for nearly every Opi-Withdrawal.
And like I stated before I guess it got so bad because you abused the shit out of it, I mean redosing every 30minutes is some serious compulsive behaviour.
I don't think it has to do with the U4 alone,(it may has its small part) but more with you smashing 700mg over a few days in these extremely short timespans.
Me and some friends never had problems like that with the substance and we are all physically dependent. Like I said, one small dose was enough for at least 4 if not 6 hours of an enjoyable buzz without the need to redose.
Waking up in hot flashes is a totally normal symptom of general opioid WD. It happened to me with Bupe, with Tilidine, hell even with Tramadol.
So I think you are wrongfully seeing the fault in the substance when it was your personal fiendish consume pattern that lead to your misery.
However I do not think that this stuff is harmless, not at all. But if taken in moderate amounts and not like Fent-Analogues or Crack it does not have this potential causing what you experienced.