I'm no longer subbed so I speak on my experience from the start of the expansion until about mid April.
It felt too short and long at the same time. Too short because due to RNG you might get the right powers to just start feeling powerful at floor 6. Too long because some floors just seemed to drag on and on without good powers. Personally I would of liked to be TC Floor 18 powerful by the time I hit floor 6 in regular Torghast.
Also in regards to powers there were not enough class specific powers. Lots of generic powers but after awhile you only really had two or three specific core class powers... not nearly enough class specific powers to make different builds