That's an interesting line of thinking. The Nightmare Court sylvari still regard the dragons as enemies, mind you, but if the Nightmare is acting essentially as a kind of safety valve for draconic corruption... that would explain a lot.
While, incidentally, humans seem to be more able to adjust to magic's inherent unpredictability on the fly by using their gut - as seen in the discussion between a human elementalist and an asura mesmer in Sea of Sorrows, presuming this isn't simply a difference between elemental and mesmeric magic. Which may go some way to explaining why human spellcasters seem to have the potential to do more impressive things without the aid of magitech or other external sources of power than the asura do.
Basically, the asura understand magic more at a scientific and logical level, which allows them to bind it into magitech. Humans seem to understand it more at an artistic and instinctual level, which allows them to do without such crutches as individuals - but means that their magic is less suited to creating a technomagical society.
There is a fairly common hypothesis that Mordremoth and the Nightmare may be connected, in part because of their shared use of husks, and in part because of the idea that once you fall to Nightmare, you can't go back.
Recent developments, however, seem to imply that it's actually the Soundless that are most vulnerable to Mordremoth. There's something funky going on with the Nightmare, but Nightmare courtiers still seem to maintain their immunity to dragon corruption.
Basically, charr are practical. They see magic as a tool to be used, not simply thrown away - however, they know that magic is often tied to religion, and tend to be a little suspicious about magic-users in general.
However, there is evidence that necromancy might actually be the most favoured magic type among (non-Flame) charr. Why? Because among charr, necromancy has generally been associated with Ash. Now, in GW1 they may well have been shamans nonetheless (with Ash shamans happening to prefer necromancy) but in GW2 we see few if any necromancers among the Flame Legion, while the Ash Legion continues to have a lot of them. It might also help that, even among humans, necromancers in GW1 had a tendency to look to expose the supposedly sacred as simply ordinary.