I can agree, Shaco is difficult enemy for jungle Nasus. You have weak early-game and Shaco can abuse your weakness. Good Rek'Sai can also get too far ahead before you get into late.

Usually people try to go for max cdr = 40%. Since you don't have neither cdr masteries nor runes you will only get 35% with Frozen Heart and Cdr-boots. Consider getting 5% from somewhere. But yea, I understand your point. It's not necessary. I also disagree with your ad-runes, I prefer attack speed runes over those. But yeah, it's your guide.

You should probably not underestimate shaco this much. He might not be able to 1 on 1 a nasus late game, but he's a very slippery counterjungler due to his Deceive. Also, you won't be able to 1 shot him with your Siphoning Strike because unless it's at least a 1 hour game in which you've been farming non-stop you just can't get that many stacks. And as I said, he's very slippery, so withering him doesn't do that much. Even if his Deceive is cooldown, chances are that he has bursted one of your carries, since his late game burst is very high, and it's hard to continue a teamfight with only one of your carries up.