Regarding the horses... this is an area that I really would love to see your talent at work,Tre!
On the first horse, the neck is MUCH too thick and short. The neck and body look more bull-like than horse-like. The leg proportions are not quite right, either, especially the rear legs. The second wireframe looks a bit better, but overmuscling would be a concern.
Just to get it out of the way, I know this is fantasy and you can do whatever you want... so please take this as suggestions and encouragement!
So, first thing first... horse bulk is inversely proportional to speed. The stockiest, heaviest draft horses are bred to pull wagons and plows, not carry warriors in battle. They look slow, ponderous, and heavy because they ARE, relatively speaking. Generally a warhorse should be as fast, therefore light, as possible, while still able to carry the warrior and his armor. Smaller horses also eat and poop less, not a inconsiderable factor!
May I suggest looking at Friesian horses for physical conformation and proportions? Friesians are considered good approximations of (and are descended from) early medieval, light armored knight's horses. They look like this:
If you want to mount up the heaviest armor guys, here's art of the Old English Black, an extinct, late medieval knight's horse, bred to carry heavy armor:
If you want to have the biggest horse, the Percheron is debatable but is a possible knight's horse... They definitely pulled wagons etc in war, but are more draft-horse than warhorse:
In comparison, Shires are examples of the biggest draft horses. They pull wagons, and they look like this:
Draft horses are always hooked up to the load by the shoulders and that is where they bulk up. All those neck and shoulder muscles are for steadily pulling extremely heavy loads, not charging at enemies.
It might be hard to get proportions correct from photos due to foreshortening effects and only being able to see 2D in any given picture. I suggest, if you can, pick a breed that works, then pick up a Breyer or Safari Winner's Circle model horse of that breed for a 3D representation. They can be a bit pricy, but you can get a smallish version pretty cheaply, and they are known for being accurate representations. I know being able to hold it in your hand can really help!
Anyway, apologies for so much info and some big photos. I hope it helps! I already love the barbarians, so give me an excuse to buy horses! Lots of horses... I'd seriously buy multiples and change out all my cavalry models! Oh, and pretty please, offer them as separate sculpts?