Well, the presence should stack, I'll check mine when I have the chance
but the Stat and Heroic Moment bonus doesn't stack with the same type of companion
Yes the presence does stack..
I LOVE my presence. I have 38 chars that have been maxed on their affection so my presence (depeding on which char I am playing) is 700-800 without adding any to my gear. It's crazy in the earlier levels. My companions can mow through anything. As I get higher levels it starts to even out a bit but they are still unbelieveably powerful.
Presence is my fav stat!