I doubt it would have been construed as equal to the written Torah before 70 (this might have sounded definitely blasphemous back then).
I agree, this does sound really anachronistic. About the prominence of the Pharisees before AD 70, what do you think of the value of Mark which was probably published in the years immediately after AD 70? The Pharisees appear therein as a significant group, particularly as disputants with Jesus about legal matters (cf. 2:24, 3:6, 7:1-5, 8:11, 15, 10:2, 12:13), and on the matter of fasting the disciples of John of Baptist are compared to them in 2:18. Whether or not the Pharisees were important before AD 70, they seem to have been important for the author of Mark. One of the really striking things about Mark is how the Pharisees are mentioned together with the "Herodians" in 3:6, 8:15, and 12:13, whereas Matthew and Luke omit each reference to the Herodians (in one instance, Matthew replaces "Herodians" with "Sadducees"; cf. Matthew 16:6 = Mark 8:15), save Matthew 22:15-16. Of course, these scenes are very unrealistic (the more Hellenistic Herodians and Pharisees were not on good terms), the lack of knowledge of Judean geography, the niceties of rabbinical debates and other facts indicate that Mark was written by a Gentile or a diaspora Jew with somewhat limited knowledge of Judea but who knew that the Pharisees, the Herodians, and the Sadducees were important groups in the country, and since he wrote before the Pharisees established themselves as the predominant sect of Judaism, this would seem to corroborate Josephus, unless Mark had similar aims for mentioning the Pharisees.
One interesting thing about the Sadducees is the anti-sacrificial rhetoric in some of the writings of Law-observant Jewish-Christians. The Gospel of the Ebionites has the following logion which was probably inspired by the statement in Matthew 12:7 ("I desire mercy and not sacrifice"): "I have come to do away with sacrifices, and if you don't cease from sacrificing, the wrath of God will not cease from you" (cf. Epiphanius, Panarion 30.16.4f). This statement echoes Jesus' statement in Matthew 5:17 that he was come to "fulfill" the Law, not abolish it, and the reference to God's wrath for not putting an end to sacrifice sounds a lot like an allusion to the destruction of the Temple cult in AD 70. A very similar viewpoint can be found in the Ascents of James. There, sacrifice was permitted by God until the arrival of the True Prophet who abolished it and the failure of Jews to stop their habit of sacrificing led to the war against them:
"And with these things he also set apart a place for them in which alone it was permitted to offer sacrifices. All of this was promulgated to them until a more convenient time should come, when they would be able to understand that God desires mercy and not sacrifices. Then that Prophet who declares these things will be sent to them, and those who believe in him will be led by the wisdom of God to the strong place of the land, which is for the living. There they will be preserved from the war which will shortly come to their own destruction upon those who because of their division do not obey. But this war did not come hastily or suddenly, as even before the arrival of the coming Prophet they had been prepared for the abolition of sacrifices...The time arrived in which that Prophet who had been proclaimed beforehand by Moses was revealed. At his coming, because of the mercy of God he first warned them to cease and desist from sacrificing. But lest they suppose within themselves that they were being deprived of the forgiveness of their sins through the sacrifices, and this be troublesome to them, he appointed baptism by water for the forgiveness of sins" (Ascents of James, Syriac version, 1.37-39).
It looks like at least for some Law-observant Jewish Christians, the memory of the Sadducees remained useful as an example of a group who exacted punishment for failing to follow the True Prophet (though the passage refers only generally to those persist in the sacrificial cult).