TTs in tbe Tour are reduced when top dogs are close in the mountains and long TTs break the GC. They increase when theres a clearer distinction between climbing based and TT based GC riders. Most important in this is the main challenger. Armstrong got the 2009 farce Schleck and Quintana got big mountanious Tours of 2010,2011,2015 and 2016. Wiggins got 2012, and the expected fight between Contador and Froome in 2013 saw a pretty well balanced route. Should Dumoulin get close enough I think he'll see better routes as ASO will likely want to mix up GC dynamics. I don't think he'll get that close though