I have the same problem: I use two to three different devices and have conflicts everyday.
It makes Evernote hard to use for me. I have to manually delete the duplicates,
Especially annoying is that if that happens to a document that you have saved as favorite. Than you have to change the favorite status to the most up dated version.
I assume that is difficult to solve for Evernote because it lies deep in their sync-logic. Or is there another reason why this problem exists that long without being solved?
I must say: I expect the sync to work. Many other tools show how its done. Like Google Docs or even Confluence. In this tools I can open Docs in 10 devices without conflicts. It is not very state of the art to have problems like that.