I see so many Dance of Knives Rogue builds online and I was really looking forward to building my own character around that skill… However, I just can’t find it no matter how many times I look in the Skill Tree. Any clues or help as to why that is? Many thanks
Dance of Knives is a new ability in the expansion. You are probably seeing folk using Flurry.
Go Furry and look at the two addons, I think its the left/ Improved furry one and you are dashed to target.
It’s in the agility skills left of dash and shadow step 
part of s6 not expansion