Excellent work. I recommend adding the descriptions of the unique abilities you get when using Valkorion's power against the Scions. IIRC one of them is a barrier, another is a unique variant of drain, and the third is the dark blast he used on Marr and Arcann.
After looking at it again, there are indeed three powers:
Dark Shield - Presumably the ability Valkorion used to deflect Arcann's lightsaber, judging from the animation.
Dark Ritual - The ability that Valkorion was using to give the Outlander his power, apparently he can also use it to drain power from the target.
Dark Blast - Definitely the power that Valkorion used to kill Marr and defeat Arcann. Interestingly, it's noted as a "telekinetic blast". This could be a misuse of the term (as frankly often happens in SWTOR) and it's just a lightning bolt, or it could hint towards relation with Kinetite, or perhaps it's the same as Exar Kun's ability and the lightning-like energy is just part of the animation.
As for the expressions of Force lightning to kill Darth Marr and defeat Arcann! Yes, I tend to get the impression that they are more then just Force Lightning.