Your build sounds decent but I would encourage you to think when other Mythics could be better. Most of the items that people are building on Live are familiar but not necessarily optimal. I'd expect them to get closer once the season starts and people have time to try out different things. Theoretically, I'd expect Rocketbelt and Night Harvester to be situationally good. (harvester if you are taking lots of group fights and Rocketbelt if you are playing against a champion that is hard to gap close against eg. Orianna, Xerath, etc.) I would not expect harvester to be performant against someone like Xerath at diamond or above as you are paying a lot of opportunity cost by not being able to force engages with Protobelt. However, if you're not that high, then kitey champions are probably frequently mispositioning, so Night Harvester might still pay off. At high ELO, I wouldn't expect that to happen as often, though. Liandrys is likely decent against multiple tanks.