When I build megatools-1.9.92-r1, it complains about missing glib-networking: megadf ERROR: Can't determine disk usage: API call 'ug' failed: HTTP POST failed: TLS backend not found, please install glib-networking. I found out, that it needs glib-networking with ssl use flag, otherwise I get the same error. So megatools should depend on glib-networking with ssl flag, then maybe you can drop the other two dependencies on openssl and glib?
I see that glib-networking with ssl depends on gnutls, so maybe openssl needs to stay.
+*megatools-1.9.92-r2 (11 Sep 2014) + + 11 Sep 2014; Yixun Lan <dlan@gentoo.org> -megatools-1.9.92-r1.ebuild, + +megatools-1.9.92-r2.ebuild: + fix missing glib-networking dep, bug 522512, thanks Jan Fikar