I did beaten all the main story, paralogue, and xenologue chapters in Normal, Hard, and Luntatic mode as of right now and I don't recall remembering that there's a single generic Wyvern Rider soldier from the Emblian Empire that was fought in the entire map in Fire Emblem Heroes. (I am not counting the recurring characters that are in the Wyvern class that fight for Veronica for the Contract) And plus, I don't see a single generic Wyvern Rider soldier appearing in one of the Grand Battles Event Maps either.
But, I also just wondered if those Generic Axe Pegasus soldiers could be actually replacing the Wyvern Riders in the Emblian Empire since this is the first Fire Emblem game that we see Pegasus Units using Axes in the entire Fire Emblem franchise and we did seen all the Outrealm characters that appeared as Wyvern Riders units that are available in the game except Spring Camilla usually have Axes?