In an of itself this understanding could not determine if such authority is good or bad. Who says unprecedented is intrinsically negative? But since those who personally accept the idea of Daas Torah tend to see themselves as staunchly traditionalist, and they also tend to feel that there hasn't been a change in the type of authority wielded by rabbis, those who argue the opposite point are implicitly rejecting the concept of Daas Torah even if, as I said, it could be correct and good even as a modern type of authority.
Not surprisingly several historical precedents have been identified by proponents of the Daas Torah type of authority, one of which is the Council of the Four Lands, or Va'as Arba'ah Aratzos (of Poland and Lithuania), a 16th-18th century Jewish governing council, which is seen as a kind of rabbinic government. For example, in an article on the Oppenheim family in Ohr Yisrael 12:4 (2007) a writer refers to the Council as one of many rabbinic synods which were customary among Ashkenazim since the time of Rabbenu Gershom (all 'sics' in the original):
באשכנז של ימי קדם קבר מזמן הראשונים כמלאכים החל מתקופת רבינו גרשון מאור הגולה, נהגו גדולי האומה אדירי התורה להתאסף מזמן לזמן לטכס עצה ולחזק עניני הכלל. וועדים אלו התקיימו באחד מערי אשכנז בהשתתפות רבני וגאוני המדינה על דרך וועד ארבעה ארצות דפולין וליטא בתקופה מאוחרת
In many other sources you'll find phrases like רבני ועד ארבע ארצות or גאוני ועד ארבע ארצות. You'll also find references to the takkanos enacted by them in various books, often Chassidic minhagim books.
Actually the Va'ad was not really a Rabbinical Congress which dispensed laws and justice, consisting of none but the gedolei hador, but a combined lay and rabbinic council. While this does show that rabbis truly were involved in the governing aspects of some Jewish communities, it also shows that they did so with laymen. (Really, really rich ones.) I suspect when pressed with this fact most who use phrases like "גאוני ועד ארבע ארצות" would disagree that it really makes a difference, since the salient point is that the great rabbis were involved in governing, but nevertheless I wanted to correct a misperception. If the idea of Daas Torah is flexible enough to include rabbis and laymen acting in concert, so be it.
Here is a page of haskama for a very famous Tanach with Yiddish translation (click to enlarge):
As you can see, the paper declares that this is an approbation of the chiefs, leaders, nobles, etc. of the Council, along with the great rabbis' ban of copyright violation. And, indeed, there are separate lists of signatures. The first are the lay leaders and below it are the rabbis. The title page spells it out clearly, הסכמת המאורות הגדולים ראש ישיבות בצירוף הרוזנים וקצינים ארבע ארצות מדינות פולין, this edition features the "Approbation of the great lights, the Gedolim, the Roshei Yeshivos, conjoined with the Nobles and Leaders of the Four Lands of Poland:
The Tanach in question was printed in Amsterdam in 1686/ 7 by the famous printer Athias. The translation itself was undertaken by Joseph Witzenhausen (יוסף בן אלכסנדר המכונה יוזלן וויצן הויזן), who saw himself as the translator from "Leshon Ha-kodesh Le-leshon Ashkenaz," with linguistic corrections by Rabbi Shabbetai Bass. The idea was to make sure that Witzenhausen's Dutch Yiddish (or German, if you will) would be comprehensible to a wider readership. It also includes an introduction by the printer, Joseph Athias, and Witzenhausen himself.
Athias's introduction has some interesting content. Firstly, he signs his name in the beginning, as follows: אמר יוסף בן לא'א הקדוש אברהם עטיאש ז'צל שנשרף על קדושת שם המיוחד. בעיר קורדובא. שנת חמשת אלפים וארבע מאות ועשרים ושבעה, adding the fact that his father Abraham Athias was burned by the Inquisition in Cordoba in 5427 (1671). His introduction is in Yiddish (or German, טייטש as he styles it) which shows that this Sephardic printer, son of a recent martyr, must have known Yiddish, which was not so common among Western Sephardim.
He discusses first of all the rabbinic explanation of Deut. 27:7 that the inscriptions on the stones refer to translations of the Torah into 70 languages. He then continues to note the great need for a translation in Poland and Moravia. He writes that because of our sins, the Written Torah is almost is if it is put into the corner. Almost everywhere in Poland and Bohemia, and other lands, the following is what happens in schools:
לערינט דער רבי איין פרשה אודר עטוואש מער חומש מיט אים דא נאך היבט מאן משניות אונ' גמרא מיט אים אן אונ' ליגט זיך אויך חריפות אונ' חילוקים אביר דאן עיקר יסוד דען באר מים חיים דיא תורה שבכתב לאזט מאן שטין
That is, the rebbe teaches a parasha or two of Chumash, and then moves on to Mishna and Gemara, with charifus and chilukim, but the main foundation, the well of living waters, the Written Torah, is neglected.
He continues to note the prevalence of Polish melamdim in the land of Ashkenaz (which I assume also includes Holland) who are ill equipped to teach the kids. He says that because of this the Torah is, God forbid, in danger of being forgotten. He then knocks the Tzeenah Ureena, which is so nostalgically remembered today because of its association with bygone beloved grandmothers, saying that it's [too] full of Gemaros and Midrashim, and translates only "al pi ha-derash." But, he says, this is not the "ikkar fun der Torah." He continues in this vein, explaining why other translations are also not good enough (don't worry, it's not all negative). He refers to the aforementioned R. Shabbetai Bass as follows
הקרה ה' לפני האלוף התורני כהר'ר שבתי משורר באס מק'ק פראג איש תם וישר ירא אלהים וסר מרע איש חכם ונבון יודע כמעט כל הספרים שלנו
He writes that he is a 'baki' in the languages of [the Jews of] Bohemia, Moravia, Austria, Poland and Germany. Since the book is being produced in Friesland in Holland, he is in a position to make sure that all the Jews of the other countries will be able to use it. He then writes some praises for R. Yoseln Witzen Hausen, the translator, and praises of this beauty of this edition in particular. Athias signs off with a note of Sefardic pride: כה דברי יוסף עטיאס מגזע ספרדים.
Here's the frontispiece, by the way, bareheaded Moshe Rabbenu, flying babies and all:
Witzenhausen too has an introduction. For his part, Witzenhausen says that bad translations are a קיין פתחון פה צו דען אומות צו געבן דאס מיר דיא תורה חס ושלום פאר פעלשן, an opening for the Gentiles to say that we falsify the Torah, God forbid, when such a translation adds more than what דער הייליגי תורה שטיט, the Holy Torah states. Therefore, he claims, he worked with painstaking effort day and night, with great depth of research and great exactness, and he went over the translation time and again so that the translation is exact without any additions or omissions.
No, this Tanach (without the Hebrew text, without any meforshim, or Targum, with these introductions) was not published in Berlin 100 years later. It is from the 1680s and has the aforementioned haskamah of the Va'ad.
Speaking of a translation which was published almost 100 years later, in the introduction to Mendelssohn's edition of the Pentateuch he includes an overview of translations which existed prior to his. He refers to several earlier editions, one of which is relevant because it is this one. Here's what he wrote:
אחרי כן נדפסו ספרי תנ"ך בלשון אשכנז ואותיות עבריות ע"י המתרגם ר' יוזל וויצנהויזן באמשטרדם בשנת תל"ט, וחזר ונדפס שם בשנת תמ"ז
Interestingly, he neither condemns nor praises it - interesting, because just prior he referred to R. Eliyahu Bachur's translation of the Chumash which he had not seen, but was severely criticized by R. Yekusiel Blitz. However, adds Mendelssohn, Blitz's own translation is terribly flawed. The Blitz translation was also published in Amsterdam a little earlier than the Witzenhausen one, and it also had a haskamah from the Council of Four Lands, albeit a less dramatic one. Thus the contrast between the way he mentions these two "Yiddish" translations is interesting. Mendelssohn knocks one, but not the other. On the other hand, perhaps the reason why he knocked Blitz specifically is because Blitz dared to criticize Bachur. Maybe if Blitz hadn't said anything he'd have only noted the existence of the Blitz translation since, obviously, Mendelssohn felt that the Witzenhausen translation of approximately 90 years earlier was also no longer adequate. I don't remember where I read this, but someone had an interesting point about the shelf life of Bible translations being something like 60 years before they become antiquated to the ears of a new generation. At any rate, from quickly skimming them I was able to see that the Blitz translation is inferior but of course they should really be examined carefully.
It gets even more interesting, because although Mendelssohn did not criticize the Witzenhausen translation - the one we are discussing in this post - the one haskamah which he received for his own Pentateuch does criticize it. I am speaking of the approbation by R. Tzvi Hirsch Lewin (also known as Hart Lyon), the Chief Rabbi of Berlin. He wrote as follows:
ועיני ראו הביבליאה הנדפסת באמשטרדם ברשיון גאוני עולם דד' ארצות פולין ז"ל בשנת תל"ט, גם זה כמו עשרים שנה נעתק באמשטרדם, וכל אלו אינם מספיקים כלל בפרט בחבור הכתובים ליישב דבר דבור על אפניו
Thus, he criticizes the quality of this translation (and Blitz's), albeit his criticism is directed mostly toward the way they translated the Kethuvim, the Hagoiographia. He continues that because only such flawed translations were available, people [now] turn to non-Jewish German translations, which are obviously far more problematic (being embedded with Christian theology and interpretations far removed from those of Judaism, although he does not say this specifically). Therefore it's great that Mendelssohn has made his correct translation . . . etc.
Here's an interesting sample from the Witzenhausen Pentateuch:
As you can see, care is taken to separate the non-German words with parentheses. Yet in some cases they are not exactly Hebrew either. So here, in Lev. 23:4 ("Eleh mo'adei adonay . . . "), we see the words "יומים טובים" used as the translation. By way of contrast, Mendelssohn translates it as פעסטע. Also, let there be no doubt that is exactly what is intended and not a typo. The Blitz translation also has יומים טובים.
In the truth-is-really-stranger-than-fiction department - in 1711 a Bible was printed with no less than five translations of the Old and New Testament side by side. The edition, called the Biblia Pentapla, included Martin Luther's translation as well as a German Catholic one, a Dutch Protestant one, and another Protestant German translation. However, the fifth one was a Jewish translation, ascribed to "Joseph Atiae." This translation is of course the one by Witzenhausen. Here is the title page, and the first page of the Bible:
In case you are wondering, in the Pentapla it says "Jomim Tobhim."
אחרון אחרון חביב, here is a page of the Witzenhausen Bible:
Yes, that's נבואה for רוח. Blitz translated it as "ווינד." Here's a link to the Blitz translation, for your reference.