I think the first D:OS isn't really a fair comparison, though, because that game wasn't as focused on the idea of custom characters. You were two source hunters no matter what, your fate was determined for you before you created your character, you just created the look and skills basically.
That's quite standard for an RPG. For practical reason you role has to be somewhat defined - Vault Dweller for Fallout1, Village saviour in Fallout2, Child of Bhaal in BGs, Watcher in Pillars, Kingdom ruler for Kingmaker, Sorcerer for D:OS2 etc. D:OS though kinda used both RPG stereotypes giving you both "Source Hunter" backstory, and amnesiac ancent generals backstory - a bit of an overkill, though D:OS story is kniwn to not be terribly well thought out.
When it comes to an act of playing I find full VO to be unecessary - first of all I want to read what I want to say: I dislike "summaries" - like in Mass Effect or to lesser extend Witcher. And if I read through lines, I won't wait for them to be read out alound again.
Something I literally just thought off, though - if Larian were to do voice protagonists it would be super nice for Coop, which might be the main reason for doing it. Player choosing the line might not care for the VO, but player "listening" on the conversation would probably prefer it to be performed.
