First item: all scripture you reference has to do with baptism... I think baptism is a form of obedience.. not required for salvation.. its a result of salvation. We can go more into this if you want, but lets stick to Baptism of the dead...
Any specific reason you think it is not required? Why would the son of God walk that great distance to be baptized by John the Baptist? Why would he make sure it was a descendant of Aaron?