I would certainly recommend trying to cut the rhizome without unpotting if your media is not too broke down to wait. I still struggle with weighing whether to repot immediately when I bring a plant home or wait til new growth season. Several new ones I have now in lava rock will be waiting til spring. I suspect this plant had issues brewing before I divided it, some sort of infection. I've been meaning to post an update because the 2 divisions that are still alive have grown very strangely. Most of the old pbulbs have died off, the leaves continued turning yellow/black as seen in my photos. There's been a lot of new growth but the new growths are severely stunted--maturing at just a few inches. This orchid was a heavy one in the beginning, so I guess its demise will just push me that much closer to orchid expert status.

Spares are always a good idea.