Dragon horns every 5 hours is too low. With hundreds of people getting maps, and then of those, people get Elders or Legendaries, there's just not enough people to go through all of the dragons for everyone. Right now on my server, we have 3 people waiting in line to release their Legendary dragons. This process will take at least 3 days to finish all 3 of those. During that time, how many more Legendary will we possibly get? How many more Elders? How many more Ferals? The point is, we will never be anywhere near close to completing them for people.
This will effectively make the Feral dragons be wasted and only Elders and Legendary be attempted. But even if we didn't do any Ferals, we may still not have enough time to go through all of the Elders and Legendary for people in our guild.
I feel that it's fine that they need so much participation to complete. However, when I can only do 5 attacks in 25 hours, that means I can't really help my house or nation very much.
In the end, I feel that the refresh rate should be cut to around 3 hours per horn.