Matt Swain wrote:So now the necrons have the void dragon in all his glory.
No, they don't.
The model the Necrons have is just a shard of the Void Dragon. We don't know if the Void Dragon is trapped in the Noctis Labyrinth, and how much of it is - it could be most of it, only a single shard, or anywhere in between.
All this changes is that the Void Dragon isn't whole.