Here is the neoFeeneyite dilemma: It doesn’t matter whether BOD is taught by Trent dogmatically or not, according to ALL post Trent theologians, the penalty attached to it’s denial is at the bare minimum, mortal sin. I personally follow Saint Alphonsus, that Trent taught it dogmatically, but because some theologians have argued that BOD is not dogma and say that it’s a ‘Church teaching’, those that deny it cannot escape being guilty of mortal sin, unfortunately.

Firstly, theologians are not part of the Teaching Authority of the Church, and are fallible:
For, together with the sources of positive theology God has given to His Church a living Teaching Authority to elucidate and explain what is contained in the deposit of faith only obscurely and implicitly. This deposit of faith our Divine Redeemer has given for authentic interpretation not to each of the faithful, not even to theologians, but only to the Teaching Authority of the Church.
- Pope Pius XII, Humani Generis, p21
No Pope or Ecuмenical Council has defined Baptism of Desire or Baptism of Blood, and they are not universal teachings of the Church.
A short list of previously held common opinions of theologians which are now heretical include: denying the immaculate conception of the Blessed Virgin Mary, that episcopal consecration was not a sacrament, and that the matter in the Sacrament of Sacred Orders was the handing over of the sacred vessels and not the imposition of hands.
Secondly, the canons of the Council of Trent clearly state that Baptism is necessary for salvation, and that the matter of the Sacrament of Baptism is true and natural water. The syllogism clearly laying it out is as follows:
Major: If any one saith, that baptism is free, that is, not necessary unto salvation; let him be anathema. (Council of Trent, Session Seven, On Baptism Canon V)
Minor: If any one saith, that true and natural water is not of necessity for baptism, and, on that account, wrests, to some sort of metaphor, those words of our Lord Jesus Christ; Unless a man be born again of water and the Holy Ghost; let him be anathema. (Council of Trent, Session Seven, On Baptism Canon II)
Conclusion: Baptism with water is necessary for salvation.