I think you're mixing up my casting of Rary's Telepathic Bond, and Morthos' own telepathy.
Rary's is two-way, within the group. Anyone can talk to anyone. Morthos' allows him to speak telepathically to anyone with a language within 100ft, but that doesn't mean they can communicate back that way.
So it would make sense to have him in, and he can relay important stuff to whoever isn't in the circle.
*Sigh* Maybe I should have waited till CL 15, when I could have 5+ myself.