I actually feel similarly, the game doesn't have all that many monsters yet there are quite a few similarities between them. They're almost separated into types, with Rathain, Rathalos and Diablos as one; Royal Ludroth, Lagiacrus, and Agnaktor as another; Barroth, Uragaan, and Deviljho are samey; and Great Jaggi and Great Baggi are like a palette swap. Even Gigginox and Barioth sometimes strike a similar pose. Alatreon and Jhen Morhan are the only two 100% unique monsters.
This is why I am interested in Monster Hunter Frontier because Capcom seems to have diversified the monster roster. I just hope they bring it over to the west for all of us to play.
Rathian, Rathalos, Barriorth, Gigginox and Diablos = Wyverns
Lagiacrus, Royal Ludroth and Agnaktor = Leviathans(new comers)
Barroth, Uragaan and Deviljho = Brute Wyverns
Great Baggi and Jaggi = some kind of derivative of wyvern species
I can not help but notice that there are way too many Wyverns. They shpuld have Barrioth a mmal and Gigginox his own species. Also, a plant monster would be kind of cool, too.