The traverse from the top of the buttress to the top of the couloir is stout class 4. Very doable with mostly solid holds but there is a ton of air under your feet. A rope would be pretty useless in my opinion. If you think you'd need one better pick another route. That being said it is a great route and a perfect way to start the traverse.
This went down in my book as one of the hairiest mothers of class 4 I've been on. Totally freaky. This was one of my favorite route I'll never do again.
doing the couloir when the buttress is right there. much better way to tour the crestones when the couloir is empty