you had a huge advantage (one mesmer still alive, so that means you either still had damage output (surge) or interupts (leech signet)) and you gave it away. You lost fair and square, don't blame the ghostly, blame your mesmer
If you watched the movie you would have realized that our only mesmer alive had been stuck in the stairs out of EoE's range. He had been stuck there since 6 minutes on the clock.
Yeah... You really shouldn't have lost. Even the mesmer wanding would have pushed the Ghostly over the edge.
EDIT: Dancing doesn't show that something is stuck, as things often clip into each other when dancing. But... You didn't even mention that the mesmer was stuck, or the mesmer at all.