The other thing I am wondering about is if the Armenians and Syrians actually had truly divergent understandings of the nature of Christ that they worked out at Manzikert, or if they had simply developed a misunderstanding of what the other believed because of using different language. Did the Armenians believe that Christ did not suffer the "blameless corruptions" that Severus wrote about, for what he meant by them? Was the understanding of what "corruption" meant fundamentally different? Was the Armenian conception of "corruption" inherently tied into sin, thus rendering "blameless corruptions" unintelligible?
Yes, you are right. The Armenians did not and do not call the "blameless PASSIONS" of the Lord "corruption". That is, hunger, thirst etc that our Lord experienced and experienced truly, not in semblance, were not corruption but voluntary acts of economy of salvation. Because, according to the Armenian Fathers, the term "corruption" is always negative and corruption is the result of sin, while in the Lord there was not sin. He took the sinful and corruptible nature of man and the mortal body but by uniting this fallen humanity to His incorruptible and immortal Divinity, he made his humanity incorruptible and immortal too, by this union already and not after the resurrection only, as most of others teach. The resurrection of the Lord brought incorruptibility to OUR bodies by grace and hope, not to the Lord's body which was the same both before and after death and resurrection. He experienced weaknesses and suffered death because He Himself wanted to, He did all those things VOLUNTARILY, not being subject to. That is, if it were His will not to experience those things, He would not allow His humanity to experience those things which were natural for it (the humanity). If He wanted not to die, He would not die. (One of the examples that the Armenian Fathers bring is Lord's feeling hunger after the 40 days and not earlier or later. He hungered only after 40 days, because it was His will to do so. Otherwise, it is not natural for us, simple humans, to feel hunger so late. They also quote John 10:18 ("No man takes it from me, but I lay it down of myself. I have power to lay it down, and I have power to take it again."). Also the words of the Lord after the Resurrection, "Behold my hands and my feet that it is I myself" (Luke 24:39), because the Classical Armenian translation of this verse translates the Greek "autos" here as the "same": "Behold... that I am the same".)
When considering the Lord's actions, the Armenian Fathers never allow any thought that could divide this union of the Lord's humanity and divinity. They consider nothing outside this union. Every moment and every act of the Lord's life on earth had as its beginning and source this union and not separately His divinity or humanity. And the result of this understanding is the teaching of incorruptibility. Because we can't consider only His humanity, separating it from His divinity. Only in this latter case could we allow the thought of corruptibility ascribed to the Lord in any way. But this contradicts to the true "miaphysitism".
Writings on this issue by the Armenian Fathers were composed not only before the times of the Council of Manazkert ("Seal of Faith" comprised by Catholicos Komitas (VII century) is devoted mainly to this subject), but later too. What I wrote above is based on one of the treatises of Hovhannes Sarkavag (John the Deacon) who lived in the 11th-12th centuries. St Nerses the Grace-filled also had this teaching. Some centuries later St Gregory of Tathev taught the same. So this teaching of the Armenian Church is very stable and hasn't changed during centuries.