Having DEPLOY_DIR_IMAGE in SSTATE_DUPWHITELIST means file overwriting can be masked out a hidden, confusing users as illustrated on IRC recently. There are only a few cases we have file overwriting in the deploy images directory left in OE-Core with the default settings, we should remove them. In particular there are multilib conflicts between: {lib64-,}systemd-boot:do_deploy {lib64-,}grub-efi:do_deploy {lib64-,}ovmf:do_deploy and if these are fixed we should be able to remove this safely for OE-Core.
http://git.yoctoproject.org/cgit.cgi/poky/commit/?id=79457a3e2b30202d3f000d87661e9d60d28f1d0b