Ok, thanks Mika! I just thought I’d stay on top of this because DreamHost support (Chris J.) told me this past Tuesday it could “take months,” which really is too long to go without caching (or EDD). Sounds like you guys are close! 
My site is actually pre-launch, so if it might be more efficient to test on my site sooner, just let me know what I can do. Otherwise, please keep me updated! I would like to engage some prospective clients after the holidays, so if it is all possible to get this fixed asap, that would be ideal so my website speed makes a good impression.
Regarding Wordfence, they told me:
"The only time we send do-not-cache headers is when:
- We send a 503 message saying access temporarily limited. (Happens when someone gets blocked)
- For a specific URL which is used to log human visits. This URL starts with /wp-admin/admin-ajax.php.
- When we serve the “You have been locked out” page if a user is locked out from login.
All other pages will behave as per normal."
So, it appears there’s a disagreement / miscommunication between Wordfence and DreamPress. Any further thoughts on this? EDD is more important to me than Wordfence, though, so please keep that higher priority. I do like how Wordfence is a free and popular WP security plug-in, but if you have any other suggestions for security plug-ins, that would be helpful.
Finally, I’ve been having a separate issue this past week. The timing seems to have started around the WP 3.8 upgrade. In short, my WP panel has been buggy, with multiple plug-ins not correctly activating/de-activating and me not being able to change their key settings. WP will say a message as if my change worked properly, but plug-ins will not have changed. Sometimes persistence or activating/de-activating in different order will do the trick. I never had any problems like this prior to a week ago.
This is a real issue, since I use plug-ins for important things like backup and restricted access, and I’m no longer able to get them working properly. I’ve tried flushing the Varnish cache, re-installing WP 3.8, switching themes, and deactivating all plug-ins (I even deleted Wordfence). I have not been able to isolate or fix the problem.
One WP expert suggested to “check your Varnish VCL script for possible issues.” Can DreamPress help me with that?
Thanks!
Tyler