Issue 8: Sheev attempts to teach Vader a lesson, to use his emotions, but to use them wisely. He warns Vader against letting himself be controlled by his feelings, otherwise his lessers will become his masters.
Issue 10: Vader doesn't heed Sheev's lesson. He allows Jocasta Nu to make him mad. First she exposes that he's Anakin Skywalker to the clones (whom he kills as a result), and then she taunts him of Sheev wanting to train other students. As a result, he loses himself in his feelings and does exactly what Jacosta Nu wanted of him: to kill her, so she can't expose her secrets to Sheev, and even to destroy the knowledge on force sensitive children. A weak old lady, Vader's lesser in every way, became his master. Sheev's warning made manifest.
This is one of the best mini-arcs we've had, let's be honest. I really like how the relationship between Sheev and Vader is being portrayed, here. In the EU, Vader was little more than an emotional bitch with Stockholm Syndrome toward Palpatine. Here we see Sheev and Vader have mutual respect for eachother, and Sheev even treats Vader like a genuine friend, even while maintaining the sharp edge of a Sith by constantly pushing and testing Vader not to grow complacent. Vader has massive flaws, but he's never weak or whiny. He makes mistakes, but he doesn't lose sleep over mustache-twirling evil Emperor doing something that challenges his morals. In fact, in this portrayal we see how Vader is more mindlessly destructive than Sheev is, which makes perfect sense, since Vader still has so much more to learn and ultimately fails at doing so.
I'll just come out and say it. The portrayal of Vader, and Vader's relationship with Sheev, is better in this Marvel comic than it is in the Dark Horse comics.