Well, first of all stop taking advices from askmrRobot. It sucks. When legion was on the stat weights were 1agi, 0.7vers, 0.65mastery and 0.61crit. Meanwhile, we've got a 15% increased dmg on both of our finishers, so IMO the mastery pulls ahead of vers. I personally go Agi-mastery-vers-crit.
In combat, I usually Shadow Blade in the opener before I go with the shadowstrikes. That ensures me that 2 shadowstrikes are enough for 6 cp so I get my nightblade up sooner. Also don't be in such a hurry with the shadow dance. I see situations in which you want to shadowstrike so fast after casting