For me it will be:
1) The Voiceover was PHENOMENAL- so many voices, new voiceactors!!! I played Female Human and April Stewart nailed this! I also heard Asura Female did an amazing job too! And again Debbi Derryberry did a phenomenal job! @Eve Eschenbacher.4201 You're amazing! BTW who is Snaff's VA?nevermind: https://www.reddit.com/r/Guildwars2/comments/9h5myf/my_favorite_communicator_dialog_so_far/e6cbve1/
2) The Music... I did expect amazing tracks, but the tracks from this episode are divine! Especially the music from Aurene's vision.
3) The map: seeing so many different environments in one map was just mindblowing! Maguuma Jungle, Orr, the shrooms from the other world, beautiful Jahai's Fortress, everything "decorated" with purple crystals. I think the designers nailed it! And the Shatterer meta is so EPIC!!
4) The story... It was the first time ever, I loved an episode from the 1st moment till the last. Everything was kept in order, it was entertaining, it was dramatic, it had so many plot twists that just blew my mind.
5) The cinematics- I think GW2 is on the way to beat all of the WoW cinematics its devs ever done! The cinematics are just perfect!
This episode was perfect, now I hope you will lead the story to the most epic events this game ever had.
Seek, and you shall find.