Legends Canon exists in the same way the Post-Crisis on Infinite Earths canon exists. It is not canon for the current storyline but that does not mean it is not in fact a well defined and cohesive canon unto itself. The Disney cannon does not officially have a name but is being called the "New Canon" by those involved with the production. What else are we going to call the old canon? The EU makes no sense. Since Legends is what all books and old properties are being labeled as, it makes sense to adopt that term as the name for the canon of old.
At any rate, we do not know how evil Vader was or was not in the New Canon. We only have four movies to go off of. In two of those he was evil (IV and V). In another he was completely angst-ridden and could easily be seen as the "ends justify the means" kind of anti hero (like Wolverine, i.e. Morally Grey) (III). In RotJ he was decidedly less overtly evil than in other films and focused on overthrowing a much more evil Emperor (a quest that can easily be seen as noble~ish).
The only real conclusive piece of evidence we have for "Vader was evil" was the episode of the Clone Wars where Anakin saw his future and labeled it as such. However, how much of that can be taken seriously since the show was basing itself off of being consistent with the Legends canon is in dispute.
The real test for determining how the New Vader will feel will be the Lords of the Sith novel and the Rebels TV show. Which I am eager to devour because I am so excited for this bold new Star Wars canon.
To the other point, because all of the Old/Legends/EU canon is being thrown out, we do not know who the Stormtroopers were and how they were recruited. For all we know, they are all still Jango Clones, in which case they were bred for war and made to follow orders. Would anyone label a Droideka as evil? Of course not. They are a tool. Clone Troopers proved they were nothing more than biological droids when they executed Order 66 without hesitation. By the same token, we do not know who manned the Death Star. There could have easily been thousands of slaves/prisoners/forced laborers. Are they evil for being forced to work on the Death Star? They had no recourse in their servitude and no hope of escape, yet Luke slaughtered them all in the name of the greater good (and presumably this would also qualify for Lando and his attack squadron when they blew up the Death Star II).
As a side note, I wonder if technical manuals are considered "safe" or whether they have been, essentially, chucked out the window as well.
1. I too miss the old canon but, we will just have to adapt. At least they are pumping new stuff out very quickly to fill the void.
3. Rebels will be interesting if only to see how the Story Team really develops the brave new world.
4. Nostolgia! Tattooine will totally be in the new film. It may be a backwater to the galaxy but it is hugely important to Anakin, Obi-Wan, C3P-0, R2, Han, Jabba and more. It is the world from which the story spring boarded. My hope is that they stay away from it in other media and focus on canonizing worlds from the Legens/EU/Old canon that never made it into Film/TV. Corellia is a great example. Birthplace of Han Solo yet never seen.