I see Luxs build Majai's all the time. Same with Akali but then again shes one of those champs that even if I shut her down early people just feel compelled to feed her.
I get Levi when I'm jungling only when I snowball early. I get Mejais on my support or mid when I'm not facing any of my counters.
If you have 5 items by 20 minutes in a SR game, yeah, you have my permission to buy Mejais.Not occult or leviathan though.