For example: EXCLUDE_OVERLAY="(layman/kde-testing)" eix-remote update eix kdevelop Still shows the version from the kde-testing overlay. If there's a new way to exclude overlays from eix-remote updates, please document it ("man eix-remote" is notable by its absence and there's nothing in "eix-remote --help" about excluding overlays as far as I can see).
Only the default choice for the virtual paths (which is autogenerated by the remote path and repository name) has been changed. You can see the paths with OVERLAYS_LIST=all eix --not So probably EXCLUDE_OVERLAY="layman/kde-testing:\ kde" or a bit more generic EXCLUDE_OVERLAY="layman/kde-testing*" will do what you want.
I suppose that the problem was only the wrong path as written in my previous comment? In this case, I suppose that I can close the bug, please reopen if I am wrong. Note that the names have changed in eix-0.19.1 once more since now the repository names are really stored as such (and not "encrypted" in the virtual path).