Armor pen on nasus
Does Last whisper work with nasus q?
Does Last whisper work with nasus q?
Last Whisper works with all physical damage, so yes.
Yes, but why would you want it? Q is free damage stack, E is free armor shred for your entire team. Why waste an item slot for 
Because enemies bulid so much armor
Again, e - free armor shred. Your job as nasus is to farm forever until you're grouped, make it to late game, push turrets and back door with good waveclear speeds and 600+ stacks pushing a turret down in 2 hits.
So your saying that last whisper is useless on nasus
It isn't useless, but it's usually not optimal. Usually you'll get a Sheen item (Trinity Force or Iceborn Gauntlet) and tank items to survive fights. Nasus usually wants to be targetting squishy targets anyways, so it's not usually that useful compared to a tank item.
I could see Last Whisper being used against a team with multiple tanks since it would increase your Q damage, which would increase your healing through lifesteal if you have to fight the durable targets.
Essentially, yes. Your job as Nasus is to be tanking damage when grouped and annihilating towers/taking attention away when splitpushing.
One of the effects of his E: ARMOR REDUCTION: 20 / 25 / 30 / 35 / 40 Compare to last whisper at: 35% Pen, 40AD. You get free AD from his Q scale.
E's also almost always the second skill you'll max, after Q. Assuming you make it to 40 minutes through the game, haven't died often and have been farming regularly, you should theoretically be upwards of 600 stacks - which works out to nearly 800 damage per strike, and with 40%CDR, that's every 2.4 seconds.
Edit: not to mention, no game with nasus should ever make it to the 40 minute mark outside of professional play.
If you are farming at a decent pace of say about 300 stacks gained every 20 minutes or faster then you reall don't get any better use out of LW.
Part of the thign thatnames nasus such a late game nightmare is that he dos build fulltank and still is able to do damage. If you get LW instead of say Spirit Vasage you will usually die a lot faster to a team with a fair ammount of magic damage making you less of a threat.
Also last I checked armor pen and reduction do not effect turrets.
But when you are doing 500+ damage with Q it is less of an issue ignoring the armor of the enemy.
Dealing with tanky enemies is what his ult's damage aura is for. Now then, at some point you might reach enough stacks that
increases your damage output vs even squishy targets even more so that
upgrades that are common on him, at which point switching might be good. In theory.
It is probably not worth giving up more than one item slot for damage at any point in the game though.
Does Last whisper work with nasus q?
Yes, armor and armor penetrations effect all physical damage, and magic resistance and magic resistance effect all magical damage.
You shouldn't get Last Whisper on Nasus though.
If you build Last Whisper - you get 40 AD and will probably die before you can do much damage with Fury, Fury's steroid, Spirit Fire, or future Siphoning Strikes. If you build full tank - Fury burns 5% HP per second and can give you up to 300 bonus AD. Siphoning's 4 second cooldown also means you can frequently use it if you're tanky enough to stay in someone's face.
If your just looking for a fun item to put on Nasus
It's not really the best item you could give him if you're looking to guarantee your win, but land that crit with your Q and tell me you don't love it :)