The Dead Sea Scroll of Isaiah represents the proto-Masoretic tradition that in some instances differs greatly from the Masoretic text.
However, what many people exposed to JW theology sometimes forget is that neither Judaism nor Christianity ever viewed the proto-Masoretic text as canonical. Canonization did not occur for either religious tradition until after the first century CE. All interpolations and redactions to the texts, both Hebrew and Christian, up to that point are accepted as part of the inspiration process, and the inspired text is only that which existed at the time the canonization process began.
This is why the Dead Sea Scroll variations are not part of the official Jewish canon or the official Catholic/Orthodox canon either. What people are looking at in the Dead Sea Scrolls is the shaping of the texts that would one day be canon, but not the canonized texts themselves.
The original texts of the Jews and Christians are not the inspired works. If the first works were then we would not have Genesis chapter 1. Matthew would exist only of Jesus' saying and no narrative. Isaiah would be a quarter of the length it is today. There would be no chapter 21 of John and no 2 Peter at all.
JW theology likes to teach that the most ancient texts were the important ones, but it is the completed works that offer the full inspiration process according to those who did the canonizing. The "drafts" may have taken generations to work through, but it is their final state at the time of Marcion Sinope's heresy that the question of canon brought the redactions to an end.
The Masoretic tradition of the 7th century was Jewry's answer to ending the redaction process as well. Thus the inspired text is that which offers a completed text, not the text in its infancy, at least not in the eyes of the religious authorities that invented the canonization process to begin with.
I know a lot of people are used to hearing something else, but that is the way it has always been. The inspired books are those agreed upon when the official discussions of canon were closed. For Jews that was the Masoretic era and for Christians it comes in two parts, the New Testament canon closing in the late 300s and the Old Testament for Latin Rite Churches with the Council of Trent (there is no official Protestant O.T. as there is no authoritative body among them to make this finalized decision--most accepting the Masoretic canon).