Hey there

the tooltip says that if I unlock in legacy all the dialogues and stories for a specific character, all others benefit from a +10 influence. Does all that influence stack? Do I gain maximum benefit from it if I have all companions "unlocked" in the legacy?

Thanks for help

Yes, that influence stacks. +10 for each individual person. But you don't get any more for completing the same class's companions a second time.

Are you really asking if seeing story content is worth it in a story-based game?

If you don't care about the story, it gives you 400 Presence for all of them. With a max rank companion, that's like a 10% bonus to Presence. Not needed, but always useful if you're doing heroics or soloing vet flashpoints.