I'm having a similar problem. All of my characters, regardless of their level, cannot summon any companions for any missions. Just like you, I could not find any solution.

" " & "Life on Mars" Not sure if anyone's chosen these?

I seem to recall "General Solo" in ROTJ commanding an assault team to the forest moon of Endor with a Jedi in the party. Han Solo a former smuggler. Technically two force sensitive companions were in the party, Leia being Luke's twin and future Jedi.

Mine is : Donhioul (basically Daniel spelled like an old Gallowgllas/Gael) From Wiki : http://en.wikipedia.org/wiki/Gallowglass