I've had to separate my three the last couple of days as they weren't getting on. Ben hated being on his own - he could see and hear the others and was pacing his cage, chewing the bars and throwing himself around! Then Garry had a go on his own - think he quite liked the peace and quiet really! They're all back together now, still a bit of rumbling/chasing etc., but nothing too bad!
I think pigs can always be paired up with another, but it would be difficult for me to get a fourth piggy (roomwise) so I understand what you're saying with the divider. And I could never disagree with boars - they're all I've ever had! :smitten: :smitten: :smitten: