Stabilizing newer version of EFL helps to clean out the portage tree a lot, and close TONS of bugs related to old E libraries, and applications. EFL-1.21 is going to be released soon and I would like to get a "fresh" start when beginning to work on it. To my knowledge, there are no build-failure related bugs open for this particular version (1.18.4). There are lots open for 1.17 and 1.20. Also, to my knowledge, you only need to stabilize amd64 and x86 in order to drop previous stable package. I tried checking if all the dependencies were satisfied, but I guess the sanity-check bot will do it better. So lets see if they are. Please, stabilize dev-libs/efl-1.18.4 for amd64 and x86 so we can move forward with E in gentoo.
x86 stable
amd64 stable