I would no more want to sit with a group of strangers on a cruise anymore than I would want another party to join my table at a nice restaurant at home. Now wouldn't that be odd!
I am one of those who have had table mates who made dinners very uncomfortable, and I also don't like being told when and where. Thank goodness we found NCL and Freestyle. Makes dinners so much more relaxing. We meet people all over the ship. And at dinner we can chat with the table next to us, or just chat with each other without having to feel we are being antisocial.