Trying to turn it off didn't do anything for us either!
Instead it kept serving up the dated RSS feed, no help at all.
What I had to do is manually go to the
wp-content/w3tc/pgcache/feed/ directory and forcibly remove the stale files in there.
Once that was done and W3TC was removed from the equation, the current RSS feed was refreshed and started being served again on its own... Hopefully it lasts once we add a new post.
But of course the feed is no longer cached by W3TC now, so hopefully this gets fixed soon so we can reenable the caching.
(BTW, did you recently upgrade from a much older version like 0.9.2.4? Wondering if our doing that might have anything to do with the appearance of this problem.)