I am more convinced now that Shatter should Beat Down the target, causing it to take 5% more melee damage, and that Impale should reset the CD on Ravage. It looks like from the Dev Stream, on November 21st, the CD on Ravage is now 18 seconds, down from 30 seconds. Impale, with its 9 second CD vs Shatter's 12 second CD makes sense to give us Ravage twice as often, and keeping Ravage central to the Vengeance Spec (now Discipline), much like Unload is to Arsenal.
From a PvP point of view, while Ravage cannot be interrupted, it can be stunned through, pushed/pulled or negated with other abilities. I see the Vengeance Discipline receives a 20% damage bonus to Ravage. This is great, but it is the ability to land as many ticks of the ability that makes it integral to the discipline. The Unstoppable (passive) Ability certainly helps but is not always possible to line up. Arsenal gets an 8 second internal CD between Unload resets, a 30m ranged ability, that with the proper utility can now be used while moving. Unload is also reset by another 30m ranged ability, while ours is reset by another 4m ability. With 15 second abilities such as Low Slash, three consecutive uses of Ravage can easily be shut down with Low Slash, Force Stun, Low Slash. This does not even include Force Wave as another means to shut down Ravage. At 11m to 30m, Unload can be used outside of the range of most abilities that would shut down Ravage.
For these reasons and those I have listed in the OP, I suggest the following:
1. Shatter remains the level 10 ability, as it makes sense with the passive DOT spreading abilities that follow.
2. Shatter and Impale should be swapped in the passive abilities that reset Ravage and proc Beat Down on the target.
The result is the Discipline path remains very much the same. Ravage CD is cut in half (9 seconds vs 12 seconds) for Vengeance Discipline. Shatter is the obvious opening ability, regardless of achieving single target or AOE damage. Ravage reset is still 1 sec longer than Unload's reset timer. This is hopefully off set by the fact that Ravage cannot be interrupted and does significantly more damage.
Second thought/suggestion:
Impale as the reset ability produces a short and simplified rotation, leaving only 4.5 seconds of GCD after Impale and Ravage are used. Where's the fun or skill in that? My second suggestion is that the damage from Ravage should be shifted so the last tick is not the strongest, as I believe it currently is. I understand that this makes sense as a cool animation, (you build your series of blows to a crescendo) but it stinks as a damage dealing mechanic in a 3 second channel. It's like, "Hey, better shut me down before I really drop the hammer on you!"
If you read this whole post, thanks for your time. I really am trying to just highlight issues and offer simple fixes to improve the upcoming Discipline (that I already love).
Good hunting!