Quote Does running extra sylvan library actually help the deck that much?
It really can. Against control, it often means 2-5 extra cards (more when they use StPs), and it usually saves you from drawing a number of worthless cards. If you have one, or can get one easily, definitely try it out.
And if you can't get a Su-Chi, I'd replace one Masticore with Phyrexian Colossus. Other TnT players have been having a lot of success with it.
I'd also definitely add that second squee, since it works well with the Masticores and makes you more resistant to graveyard hate (plus it lets you totally abuse Survival late game).