User blog comment:Commander Marko/The advantage of Duo Queue/@comment-4888212-20130922014427/@comment-22338397-20130922180701

That last part is definitely true for Normal Draft, where the position of Team Captain is randomized. The party leader absorbs the chance of his premades being Captain, so that in a 5v5 match, the leader of a 3-man premade will have a 60% chance to be Captain, for example.

I don't think that's the case for Ranked play though, especially since I still was firstpick twice, even though my partner invited in those cases :)