This is patch 5.1, I can confirm the mount still drops on both 10 and 25-man versions of the raid. They have the exact same chance to drop so don't waste time soloing 25-man :)
This is patch 5.1, I killed Malygos 10-man last night and I can confirm:
Both mounts can drop from a single kill, and Azure Drake also drops from 10-man! Submitted a screenshot as proof.
Edit: Apparently my screenshot didn't get approved. Here is the link to it: http://i169.photobucket.com/albums/u210/dragancla/wtf_zpsdb4caaf3.jpg