In multiplayer you do actually hear the main character voices when you speak to other players, its pretty nice.
They had this mechanic in Divinity as well, where after certain story hooks had unfolded, you would be prompted to talk to one another. Those lines were voiced as well, as were certain interactions and reactions in the open world... so yeah, same as in BG3 now, I guess, which I still think is a damn shame. I really hope they end up voicing the entire dialogue system, I'd personally be more than happy to sacrifice a bit of content to have it fully voiced
