I would say 10 men is a reasonable number for such a large forest and such dangerous enemies. However it's still large for normal assassin squads in my mind. But like i said this is a special case so it should be fine.
In that case i don't like the assassin's chances. Kris, Jason, Phenom and Otori are all At Jason's house where they are headed. 4 against 6 assassins with the possibility of Seki waking up. Doesn't look good for the assassins.