All conversations should be based on the group present for the conversation.
In some cases, a companion might interject on their own.
In other cases, maybe you can take the option of getting the help of a companion who would be more persuasive (or the one with pet pal) -- without exiting the conversation.
There are plenty of situations in this game where the character to speak to the NPC will just be the character who coincidentally is closest to the NPC.
Also, don't you think it's weird if a group of adventurers approach a merchant, and the merchant suddenly forgets he hates three of them because the fourth one hasn't done anything bad yet?
