They sure did mess up a bunch of battles. They limit the weapons to. Green beret vs Spetsnaz, Ninja vs Spartan. Anyone who knows anything about special forces knows that Green beret are sent into to create militia armies out of natives and don't generally engage the targets themselves. If anything since Spetsnaz is Russia's elite it should have been delta force or another tier-one group. The best of the best of one country vs the best of the best of another. At the very least the rangers should have been used since they directly engage targets. Real ninjas back in the feudal era wore a variant of samurai armor not all black outfits. Thats a misconception and is due to Kabuki plays that display them as such. They also let fake ninja's do all the weapon selection. There is only one known true ninja left and he probably refused them so they got the fakes who don't know crap about real ninjutsu. Another thing ninja's did not engage in straight forward combat he would have attacked and ran to cover and then attacked again wearing his opponent down while setting him up for a trap. Vampires will pwn Zombies, I mean come on a slow dead corpse vs a shape shifting, super fast, super strong vampire who can also fly. One on one Vampire has it but if its like L4D and they are uber fast they might win with swarm factor. The day there simulation program can handle warrior types and allow parameters to expand and control the types it will never be a true to life battle. When I say type I mean stealth, guerilla, etc...
