Isn't it still hubris?
Darth Vader: As a knight of the Sith he felt he was beyond the teachings of Ben Kenobi and thus is defeated by a lack of faith in the Force (this is setup early on). Ben came back more powerful in that he could guide Luke into destroying the Death Star using faith to do what raw power and technology could not. Vader felt the force was powerful but felt there was nothing beyond his own power, and not even he could save the battlestation.
Tarkin and his fellow officers felt that while there could be a weakness to exploit, the Death Star was still powerful enough that it didn't matter. Tarkin doesn't leave after he is informed there was a risk of the Rebels destroying the base since they continually failed to do so, thus cementing the view that the Death Star was unstoppable.
Regardless of any weakness the Imperials remained confident. Only Darth Vader is the one who truly sees the risk for what it is, but even then he views himself as powerful as the war machine he is here to protect and ultimately isn't.
Galen being responsible for the weakness does not detract from that because it ultimately didn't matter. In Tarkin's case the Death Star was a moment from firing thus Luke almost failed, and in Darth Vader's case he still fails for a lack of faith in the force, something he realizes he is lacking in when he is about to shoot down Luke.