I've had the same problem. None of my completion times are showing up in the leaderboards. I've completed Iron horse multiple times in approx. 2 hours and my time never shows up. There were no player swapping, disconnects, or anything out of the ordinary during the raid.
Sent a ticket to Ubi and the response was : ''Thank you for reporting this issue to us. We have forwarded this for investigation.''
Hope they figure that one out.