Hello ...
According to what he said, I have the impression that the problem is only in the html of your template. Where tells page that should keep or not the cache. You should know that there are 2 types of caches, the site, which is on the client computer itself, and the site, which is used by the site to store information and send it to you without the prior processing.
What happens in the site header, the information dealing with the cache, are not correct. It is only correct, and clear the cache. I do not like the W3 Total Cache, too bad, I use another.
I have experience with a site that come 1200 people a day, and web cache. If you do not have the cache, is slow and decreases the number of people who can visit you in addition to weigh on the server.
At.
Daniel Cesar