The Sanctus, in Latin or Greek form, has apparently been part of the Mass since at least the 5th century. Doing a quick bit of research doesn't clarify for me whether or not commas existed either when it was written or when it reached its final form (in Latin). I need, therefore, to simply go back to the Sanctus as it's printed in the Latin Roman Missal:
Sanctus, sanctus, sanctus Dominus Deus Sabaoth.
Holy, holy, holy [is the] Lord God of Sabaoth.
(I'll come to Sabaoth in a minute.)
In the earlier phrasing which you refer to (the 1973 translation made by the International Committee on English in the Liturgy, or ICEL), we had
Holy, holy, holy [is the] Lord, God of ...
The syntactic difference here is whether "God" is part of an appellation—"[the] Lord God"—or whether it's an appositive—"[the] Lord, [who is] God of ..." In the Bible, "Lord, God of ..." is typically (but not always) used to address God:
LORD, God of hosts, who is like you?
(Psalm 89:9; this and subsequent quotations from the New American Bible, Revised Edition)
"Lord God of" is typically used to describe God:
Today belongs to the Lord GOD of hosts ...
But there's a bit of switching between the two, which leads me to feel that there's no significant syntactic difference between them.
Now let's get to Sabaoth. This is a transliteration (used in both the Greek and the Latin texts of the Sanctus) of the Hebrew word צְבָא֖וֹת, which is elsewhere translated "armies" (or "hosts", which can be used as a synonym)—see for example the BibleHub.com analysis of Deuteronomy 20:9 in Hebrew.
Though I cannot find a reference to the ICEL's reasoning in their translation, it seems fairly obvious that they were trying to find an equivalent to this word "armies"; they appear to have gone with a metaphor. There is some Biblical support for this interpretation in, for example, Judith 9:14:
Make every nation and every tribe know clearly that you are God, the God of all power and might ...
as well as, more famously but less directly, Revelation 7:12:
Amen. Blessing and glory, wisdom and thanksgiving, honor, power, and might be to our God forever and ever. Amen.
But "Lord God of hosts" is much more common, and actually appears in Isaiah 6:3, from which this part of the Sanctus appears to be taken:
Seraphim were stationed above; each of them had six wings: with two they covered their faces, with two they covered their feet, and with two they hovered. One cried out to the other: "Holy, holy, holy is the LORD of hosts! All the earth is filled with his glory!"
Thus "Lord God of hosts" appears to be the more exact translation, and is used in accordance with the norms of Liturgiam Authenticam, a document produced by the Congregation for Divine Worship and the Discipline of the Sacraments, which includes the following text:
While it is permissible to arrange the wording, the syntax and the style in such a way as to prepare a flowing vernacular text suitable to the rhythm of popular prayer, the original text, insofar as possible, must be translated integrally and in the most exact manner, without omissions or additions in terms of their content, and without paraphrases or glosses.