The Scotist theologian Claude Frassen (d.1711) who was post-Trent, and an expert in the writings of Blessed Duns Scotus, devoted a whole chapter in his tenth volume to the question of the necessity of baptism (De necessitate Baptismi). Without giving the whole article, I translate his first conclusion:
"Baptism is necessary by a necessity of means for all men, whether adults or children. This is determined de fide from the Councils of Milan and Carthage, as Augustine puts forth, Epistle 90, and 92, and from the Council of Trent, Session 7, Can 5., 'If any one will have said, that Baptism is optional, that is, not necessary for salvation, let him be anathema.
But the truth of this conclusion is gathered from the words of Christ in John Chapter 3, 'Unless you will have been born of water,' etc. By such words Christ the Lord signifies, after the promulgation of the Law, that no man is able to gain eternal salvation, unless he will have been born by the water of Baptism. Such is the teaching as laid forth in Tertullian in his book concerning Baptism, ch. 12, where he says, 'It is prescribed, that no man is able to achieve salvation without Baptism, from this, primarily from the words of Our Lord, 'unless you will have been born again from water, you will have no life.' Hence the chapter following he (Lord) is speaking concerning those who assert that faith suffices for salvation...By these words (Frassen continues) Tertullian very patently reveals the impious assertion of the Calvinists, who contend that man is able to be justified, even without baptism."
Later in the article Frassen dissects the words "unless a man be born of water and the Holy Ghost," commenting that all the fathers (omnes SS. Patres) take the conjunction 'and' not as a disjunctive, but as a copulative word, meaning that both faith and water are necessary.