I've played Divinity original sin 1 and 2 with a friend and sometimes 2. It is in my opinion one of the greatest things about the games.
I might have mistaken what was said about multiplayer, but it sounded like they want us to experience all the companions etc and their stories before doing multiplayer.
When I heard that multiplayer will not be in the game at first, I was kinda let down. I cannot see one single downside with having multiplayer. Yes, if you play multiplayer, you might not get the full experience with all the characters in the game, companions etc. But you are not forced to play multiplayer, play singleplayer if you want, and experience it all on your own.
But what about guys like me, who really never play singleplayer games. I firmly believe that games are meant to be played with friends, and they did the multiplayer in Divinity Original sin 1 and 2 so good, it was awesome! I will buy the game when multiplayer releases, and I will play with my friend, but he is going to play the game at release, single player, and I won't.
So my friend will have played the game for some time before I will, cause of no multiplayer. This means that me and my friend will not experience the game together as it should be experienced, He will know most of the mechanics, companions and a lot of the game itself. So we will not have the laugh of doing something stupid in-game that possibly kills us all, or talking shit to some goblin, making them hate us. We will lose so much of the fun, because we can not experience it together.
My point is that multiplayer is and will be one of the greatest thing this game will have. Look at it this way, try playing the tabletop Dungeon and Dragons alone.
Yes, these are all my opinions and may not be the same as yours. But please don't force us to play single player, let us decide ourself if we want to play single player or multiplayer, even if we miss out on some content. We will probably play through more than once.