I would like to see that Dean’s responsibility for breaking the first seal is taken into account as well

Right? Instead of telling Sam that he's helped more people than he's hurt, maybe Dean could say, "Hey, you weren't alone in that, Sam. Me, Cas, the angels, everybody played a part in letting Lucifer out of the cage." I mean, why the hell can't he take responsibility for his role in how things played out? Until he does, his reassurances will sound hollow. He's still allowing Sam to take the fall for it.