Optimal build for caster nasus?

Normal Nasus is played as bruiser/tank but with the current pre-season there's a lot of ranged top laner so I'm forced to play Nasus as a caster in-order to get any amount of farm. During season 5, I used to go tear -> rylais -> luden (pre nerfed) -> sheen -> liandry -> finish lichbane -> tier 3 boots -> finish with muramana.

The problem is in this season, champion has more sustain, so I can't really just poke them out of lane anymore with max'd E so I went with a new build. http://i.imgur.com/kovHqvJ.jpg Tear -> glacial shroud -> sheen -> boots -> rylais -> liandry -> FH -> finished muramana -> finished IBG.

It kind of worked, but I don't feel it being optimal for caster Nasus. Any dog mains want to tell me build path if I get counter picked and need to max E first for farm?