Eorlund and Fralia Gray-Mane have somehow become died for for unexplainable reasons over the course of the game I've been playing for over a year. It's possible they fell from from the sky and I didn't realize it. Another possibility is that they became stuck underneath the playable area of the city. Recently I saw a Whiterun guard fall out of the sky and die on impact below the steps up to Dragonsreach near the temple.
I realize these deaths are due to an engine bug, but would it be possible to investigate whether a failsafe trigger could be added under part of Whiterun like was done in Solitude? I don't think Whiterun is as bad as Solitude, but it also spans several cells and seems to be prone to the same problem. Not that UESP is always reliable, but people there have also reported both Eorlund and Fralia dying for no apparent reason.