Everything said before me is spot on, I cant think of anything else to add besides I personally feel 0/9/21 is best for Nasus because he is extremely survivable without a full defensive tree.

building bloodthirster is really unnecesary, just go straight for the warmogs, and I would recommend 0/21/9 for your masterys. the whole point of nasus is that he is unbelievably tanky, you dont need any more damage output than an insanely farmed Q gives you. also exhaust is next to useless on nasus as you have wither, which is basically exhaust. ignite is also not terribly useful, i would run flash/ghost or flash/tp.

and oh my god those runes are dreadful. even if you mean greater they are still pretty much useless.

nice runes man

You lack some information about Items, and I think Exhaust + Ignite is an overkill... I would use one of them, since Nasus hasnt got any escape mechanism, and he needs sth. like flash to escape gank.
And last i would recommend using a 21/0/9 Mastery tree, since for me it just does the job way better.
So all in all: More information, and maybe some changes in your Sum. Spells and MAsteries. The rune thing is the same, i wouldn´t split Runes (4 of this 5 of this) and always use Greater runes.

You have 6 points in Spirit Fire and 4 in Wither.
BB coding errors as well. If the guide is not finished you may consider archiving it until it is done.
Also, I doubt anyone will be using lesser runes for their builds. Even if you have not acquired enough IP for the greater runes i suggest still putting them in your guide.