Do others followers (e.g. Leah, Tyreal) that join you in some parts of the story have special abilities (buff, active skills, etc.)?
Aside from cinematic powers, the answer thus far appears to be no, unless they're very well hidden.
Though do be careful - they have the power of being willful jerks, and Tyreal really loves to pull Champion packs or attack treasure goblins you weren't quite ready for.