First up, I absolutely love the plugin and have been able to reduce load time significantly. I currently use a VPS with 2GP or RAM as well as Maxcdn.
Here's my issue (full pingdom report at the end):
At this point, I'm mainly concerned about server response time which has been awful (1.5-2 secs). With page caching set to disk enhannced and database caching set to APC I've gotten server response down to about 0.8 secs (see pingdom report below).
The problem, however, is that as soon as I use those page caching settings my adserving gets screwed up. I use two ad networks and impressions served (default and sold) drop to about half of their normal values.
I've tried this out several times now. Using W3's best page caching settings for my site increases load times and site speed which results in higher pages per visitor driving better engagement. That's all great, but ad impressions served drop alongside each time I see these site performance gains.
Any help on this would be really appreciated, I've been battling with this for weeks, even tried out supercache with no success.