Worst die-off I've ever seen in TN was the 2007 outbreak. I was assisting the TWRA with their thermal imaging surveys at the time, and we were doing Williamson County. At night, you could tell how close we were getting to a creek or pond by the gagging stench of dead deer. The next year, in eastern Williamson County, we couldn't buy a deer sighting using thermal imaging. I suspect that area experienced a 70-80% die-off. Over in western Middle TN, centered on Hickman County, I suspect most herds experienced a 30-50% die-off.
I haven't seen anything like it since, although I heard from clients in the Hickman and Perry County area that they felt they had an equal die-off in 2019.