Okay, so this entire event drove me nuts. I had NO idea why this event happened – and I felt the lackluster attempt to make this some kind of lore seemed like they were reaching. Anyways, I sat back and started asking questions, clearly they were trying to tell a story because there were things that happened during the event that were obviously references to something. So I answered all my own questions by researching.

1) Why did the Horde attack Theramore?
Simple. Garrosh is WoW Hitler.Every time this orc gets into anything he is Hitler. If you think of him that way – his actions start to make sense.

2) How did I get there on my Horde toon? I assume he didn’t open a magical panel and selected “Theramore Event” as an option… as that would break game immersion.
You are one of his Kor’kron agents. If you don’t know who they are look them up.

4) Who is Thalen Songweaver?
A traitor Sunreaver who was sent to aid Jaina by the Sunreavers in Dal.

5) Was the whole point of me going to Theramore on a Horde toon to rescue Thalen Songweaver? I see no point of me actually going there if a zeppelin was going to just bomb the place…. so…
Because he was an asset.

6) I was under the impression that demonic practices were forbidden in Orgrimmar–Why are there Orc Warlock NPCs?
They aren’t forbidden, only barely tolerated.

7) Why is Jaina’s hair white?
Mana bomb arcane magic.

8) Why is there no story to this event?
Blizzard can’t read a book.

9) Thalen? I don’t really understand. What about him being a traitor. What did he actually do to get tied up?
He was sent by Rhonin and Aethas as a good will gift by the Sunreavers, but he was working for Garrosh against Theramore. He weakened the gates of Theramore, until Jaina knocked him off the walls, and locked him up in Foothold Citadel.

Ya. That basically sums it up pretty good.