I've seen Hamilton twice, and here was my experience:
The first time, a matinee, only Daveed, Chris Jackson and Andrew Chapelle (who went on that day as Mulligan/Madison) signed autographs. Chris was in a hurry to get to one of his kids' events, but he still signed for every person there (and it was a mob scene), though he didn't take photos. Daveed took his time, joked with everyone and took lots of selfies.
The second time, several performers came out - Lin, Oak, Daveed, Rory O'Malley, and Leslie.
None of the ensemble and none of the women came out either time.
Biggest gripe is that the stagedoor gets packed with people who didn't see that show. So even if you're the first one out the door, there's already a mob there and you can't get close. I think this limits the number of performers who can handle coming out to face the crowd. On the other hand, the performers who do, make it to every single person there.