Tried it toplane with grasp, I went RoA into demonic (with bami's cinder inbetween) and then tank items (spirit visage and finished sunfire), the build feels super nice! A lot of sustain, good tankiness and decent damage, makes rakan feel like a bruiser with lots of mobility. At some point I was even 1v2ing a singed+alistar and managed to bring them to half health before disengaging with ult and ghost.
If you're really fed I think a slotting a dark seal in there would be amazing, the healing with q and RoA passive is really good and grasp and overgrowth got me to almost 5k health at level 18, will definitely play it some more, at least until they inevitably nerf rod :S