From what I've seen, they are much more balanced in 0.87 now.
Not every troop and their dog should think they need to be mounted.
Horses and Wargs are now a commodity based upon scarcity and that is awesome!
Quoting random_thoughts_7,
A horse shortage could create interesting ways to overcome it. For example there could be a horse-lord faction that gets +1 horses/turn. This would give them an all-horse army if they wanted it and opportunities for trading with other players.
Or there could be quests with the reward of a number of horses (eg 30), or a new horse resource, at the end of it.
Or there could be a research option to increase horse numbers, or a building for the same thing. Or a magic spell ...
Awesome ideas!!!
I would also like to add that, now with Horses and Wargs being more scarce than before, this opens up the door for fantastic mounts! Being able to find a Unicorn Grove or a Griffin's Roost and have them outpost scarcer amounts of mounts relative to horses or wargs, but enough to that the player can fully explore having the new tech "Fantastic Mounts", being researchable right after 'Warg Riders'.
Unicorns should have the ability Teleport: 5 turn cooldown, Unit is able to teleport anywhere on the tactical map.
Griffins should be flying units, able to traverse strategic terrains that would otherwise inhibit movement.
I welcome other suggestions for fantastic mounts....