No DA revolver ever made featured a 5.5 pound primary trigger pull.
The fact that Glock's design features and quality allowed them them to win the Austrian military pistol competition, the fact that they were designed in such a way as to allow them to be produced cheaper than any other serious military pistol, had a lot to do with it.
The fact that fully loaded with 18 rounds, a Glock 17 weighs less than most loaded six shot revolvers, is a big plus.
You are correct, no DA revolver ever made featured a 5.5 pound double action pull. This is an advantage to the Glock. Their "Safe Action" gives most of the advantages of a double action pull with out the disadvantages.