Regarding the Epiclesis,
From my reading its seems that the West did have an Epiclesis but about the Fifth Century it was moved, and perhaps split up, to before the Words of Institution, in line with the Western emphasis.
“Veni, Sanctificator omnipotens aeterne Deus. et bene dic hoc sacrificum tuo sancto nomini praeparatum.”
“Come, O Sanctifier, Almighty and Eternal God, and bless, + this sacrifice prepared for the glory of Your holy Name.”
“Quam oblationem tu, Deus, in omnibus, quaesumus, benedictam, adscriptam, ratam, rationabilem, acceptabilemque facere digneris,. ut nobis Corpus, et Sanguis fiatdilectissimi Filii tui Domini nostri Jesu Christi.”
“O God, deign to bless + what we offer, and make it approved, + effective, + right, + and wholly pleasing in every way, that it may become for our good, the Body + and Blood + of Your dearly beloved Son, our Lord Jesus Christ.”
There is no sense that the Spirit’s blessing of the Gifts is not still required in the Roman rite but only it is not directly invoked at particular point after the Words of Institution, as it is in Liturgy of St John Chrysostom. Also, in the West the Liturgical action, according to Nicholas Cabasilas, was not complete until after the prayer:
“Supplices te rogamus, omnipotens Deus, jube haec perferri per manus sancti Angeli tui in sublime altare tuum, in conspectu dininae majertatis tuae: ut quoquot ex hac altaris participatione, sacrocanctum Filii tui Corpus, et Sanguinem sumpserimus, omni benedictione coelesti et gratia repleamur. Per eumdem Christum Dominum nostrum. Amen.”
“Most humbly we implore You, Almighty God, bid these offerings to be brought by the hands of Your Holy Angel to Your altar above, before the face of Your Divine Majesty. And may those of us who by sharing in the Sacrifice of this altar shall receive the Most Sacred + Body and + Blood of Your Son, be filled with every grace and heavenly blessing, Through Christ our Lord. Amen.”
He considered this to be the “Epiclesis” and from it that the Latins were incorrect to consider the change complete before this time, otherwise there would not be an imploring for God to accept the offerings to be brought to the Altar, which would be tantamount to blasphemy because they would already be so, being the Body and Blood of the Lord already accepted. This prayer is in contrast to a similar prayer in the Liturgy of St John Chrysostom that presupposes the change of the Gifts before the prayer:
“Ὑπὲρ τῶν προσκομισθέντων καὶ ἁγιασθέντων τιμίων Δώρων, τοῦ Κυρίου δεηθῶμεν.
Ὅπως ὁ φιλάνθρωπος Θεὸς ἡμῶν, ὁ προσδεξάμενος αὐτὰ εἰς τὸ ἅγιον καὶ ὑπερουράνιον καὶ νοερὸν αὐτοῦ θυσιαστήριον, εἰς ὀσμὴν εὐωδίας πνευματικῆς, ἀντικαταπέμψῃ ἡμῖν τὴν θείαν χάριν καὶ τὴν δωρεὰν τοῦ Ἁγίου Πνεύματος, δεηθῶμεν.”
“For the precious Gifts, which have been spread forth and sanctified, let us pray to the Lord.
That our God, who loveth mankind, receiving them upon His holy, most heavenly, and noetic Altar as a savour of spiritual sweetness, will send down upon us in return His divine grace and the gift of the Holy Spirit, let us pray.”
This prayer is reflected earlier in the service for the preparation of the Gifts:
‘Αὐτὸς εὐλόγησον τὴν Πρόθεσιν ταύτην καὶ πρόσδεξαι αὐτὴν εἰς τὸ ὑπερουράνιόν σου θυσιαστήριον.”
“…Do Thou Thyself bless this oblation, and receive it upon Thy most heavenly Altar…”
which is much in line with the prayers in the Roman rite.
Thus, the two rites are very similar and the anaphora properly concludes with a prayer after the Words of Institution. The Roman rite in this is not different from that of Constantinople and the issue is not so much the words of the rite but the interpretation.
Note: I am opposed to any artificial inclusion of an Epiclesis in the Roman rite as used in Western Rite Orthodox Churches, because of the above.