So, I've been doing more thinking than I should be lately. The substance of my brain fever is the sylvari immunity question, which has always been a conundrum that never quite worked it's way out of my head.
Here is some postulation that's a bit out there but might just work: We believe that the sylvari are immune to Elder Dragon corruption because the Dream protects them. However, what if the Dream isn't quite the reason?
Here's the theory: Some of the playable races were seeded through the Bloodstone, before the gods found it. The sylvari were seeded through the Maguuma shard, after the gods split the stone into five pieces. The Maguuma shard was aligned to Mordremoth. Ergo, the sylvari are immune to the corruption of all but one of the Elder Dragons because they've benefitted from the spell, cast by the gods, that sundered the Bloodstone into five pieces.