I can also confirm this situation that causes the app pool to crash. We have a site running several CF apps under the same app pool for a good 6 months and have never had an issue with the app pool crashing. If I attempt to create an additional app pool on the same site even for another CF app, it will crash almost immediately once the site using the new app pool is accessed. So it seems, at least in my case anyways, it works fine as long as only one app pool is configured per website. I get the same "Load balancing workers will not function properly" error in the redirect.log if more than one app pool is used.
Some things interesting to note that I have discovered over the past few days to prevent the app pool from immediately crashing upon page visit ( I don't know long term as I only have been testing on our dev box) is that if the additional app pool being created is for an ASP app, enabling 32-Bit applications on Advanced settings for the ASP appool seems to not cause the CF app pool to crash. Secondly if the identity of the CF app pool is changed to a higher privileged account such as Local System it does not seem to crash either. But for security purposes though, this is not acceptable, just something interesting that I noticed.