Xerath Build S6?
I've always liked Xerath, but as of now, I question what to build on him. Generally you build:
• Morello/Athene's • Sorc's • Luden's • Void Staff • Rabadon's • Zhonya's
This build gives a good amount of poke/utility, but what about the following build?
• RoA • SE • Sorc's • Rabadon's • Rylai's/Liandry's • Zhonya's
This build gives pretty much infinite mana, HP stacking, and fantastic scaling. It gives Xerath a lot more tankiness that he doesn't have. The HP, mana shield, and Zhonya's could save him from assassin dives too. He also scales quite well lategame, so I figured RoA and SE would serve well.
What should I build on Xerath as of now?

(instead of

I build this early if I'm needing some survivability against an AP assasin


This is my favorite item to whip out later in the game for my 4th item or so. Xerath is already pretty good at peeling when played well. This item makes hitting skillshots and peeling stupid easy. Best feeling is landing your first ultimate and then the next 2 are easy thanks to the slow. Plus the health is nice for survivability. ALSO, now your ultimate can be used as a long distance catching/ initiating tool.
_ I haven't been able to play test this yet but I see it being used by others and I think it suits Xerath quite well. Extra money, extra damage (champions and towers), more peel during ganks. Also I imagine the active compliments your ultimate extremely well seeing as they will likely need to blow flash to avoid your ultimate shots if slowed by the ghosts._