Really? Are you not aware that the LXX is a CORRUPT Greek translation of the Hebrew Tanakh? The King James translators said so in their Preface, and many others who came later have also pointed this out:
"Yea, Epiphanius above named doth attribute so much unto it [i.e. the LXX], that he holdeth the Authors thereof not only for Interpreters, but also for Prophets in some respect; and Justinian the Emperor enjoining the Jews his subjects to use especially the Translation of the Seventy, rendereth this reason thereof, because they were as it were enlightened with prophetical grace. Yet for all that, as the Egyptians are said of the Prophet to be men and not God, and their horses flesh and not spirit [Isa 31:3]; so it is evident, (and Saint Jerome affirmeth as much) that the Seventy were Interpreters, they were not Prophets; they did many things well, as learned men; but yet as men they stumbled and fell, one while through oversight, another while through ignorance, yea, sometimes they may be noted to add to the Original, and sometimes to take from it; which made the Apostles to leave them many times, when they left the Hebrew, and to deliver the sense thereof according to the truth of the word, as the spirit gave them utterance. This may suffice touching the Greek Translations of the Old Testament."
Adding and omitting from Scripture -- as done by the 70 -- is simply corrupting the Bible and God has forbidden it. And furthermore adding all the Apocryphal books to this translation in itself is MAJOR corruption. According to the Lord Jesus Christ there are only 24 books in the Hebrew Tanakh -- The Law of Moses (5 books), the Prophets (8 books), and the Psalms (11 books).
And he said unto them, These are the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in [1] the law of Moses, and [2] in the Prophets, and [3] in the Psalms, concerning me. Then opened he their understanding, that they might understand the Scriptures (Luke 24:44,45) [Note: "The Psalms" is named for the first book in that grouping, which is also called "the Writings"]
So any claims about the "excellency" of the Septuagint are bogus.