[snakes1100]

As one particular part of your question was a bit confusing, can you clarify a bit more on what you mean here?

We've had to do some changes to make vBulletin behave like we want for example change the X-Real-IP header to Remote Host as well as X-Forwarded-For.
This makes us see the actual clients IP address in the access logs on Server2.

As i run numerous simular setups with nginx doing a lb, i do it a little differently, in most cases, when the servers are on a gigabit switch or close enough for nic to nic.

Server 1:
Nginx Front End - Proxy LBs to both servers
Apache backend (mod_rpaf installed)
All files kept on server 1 for site(s)
NFS

Server 2:
Nginx Front End
Apache backend (mod_rpaf installed)
No Site Files.

mod_rpaf would resolve all IPs to the actual client IP in the access logs of apache.

In two cases of the above setup for the owner that wants Stats for the site, the apache logs files are merged together daily via cat & cron.

As rsync is faster, in the above cases i dont have to worry about any cron issues, file problems, date stamp etc, but i do rsync in a few cases as well using smaller drives, as there is no space requirements.