They should be fine. Miscanthus can live for years without dividing, however all the healthy growth will be on the perimeter of the plant with the center being all old dead growth. Like a big donut!!

Use a saw and cut pie-shaped wedges out of the plant in spring. It is far easier to divide the grass in place rather than attempting to dig up the entire rootball - it is very dense and very heavy! Then just discard the dead interior.

Thank you for your prompt reply. I'll grab pictures this year and use as a reference for next when I cut out the old. For some reason I was thinking lifting them out of the ground and replanting the good was doing something. Leaving in place is much better! Thanks again