I would change the marks out for ArP marks. Spirit Fire dmg is not a game changer aside from the - enemy armor, and the MrP marks don't really help Nasus in any other way.

I feel maxing siphoning strike first is more beneficial, IMO pushing solo top is not ideal for a Nasus who needs to farm his Q, and spirit fire will waste a lot of minions allowing you to Q less of them.

The CDR on leveling siphoning strike helps a lot with the farming as well, not just the teamfights, which also makes it a lot more viable than maxing spirit fire.

Perhaps go with alternating between the two spells each opportunity keeping SS one above Spirit Fire, giving you the pushing ability you seek, and the low CD time of siphoning strike.

As a personal preference I like a 0/9/21 mastery tree, because IMO Nasus is tanky enough with his passive and ult without warranting the full defensive build, and all the utility masteries better suit Nasus (more skill spamming, movement speed, increased buff time, etc). BUT if you stay 0/21/9 I would look into getting a point into Defensive Mastery or maybe even 2, with solo top the reduced damage from minions can be the difference between death and escaping if you get ganked, and the Harden Skin boost really drops off after level 1.

I want to wait until I vote to try out this build more and you reply to me. And obviously all these tips are just personal preferences, just offering some constructive criticism based off my experiences thus far. Overall Good Job!

Thanks for your response but as I said, as a tanking Nasus rushing Trinity force sacrifices alot of early game survivability. Better live and do ok damage than die and do no damage. Thanks for pointing out the cooldown reduction per point however as I had slightly overlooked this.

Great guide, but I still think you should level your Siphoning Strike up first, because if you get in any teamfights while your lvl 13 or something, your Siphoning Strike will not be able to be spammed at people as if you were to level it up first then if you were to max it at level 18. And I think Trinity Force should be your first core item to do even more damage with it.