If they were movie threads, they are in the movies section. (if there is one specific one that is actually a tutorial and very clean - not heavy metalpoloza on ice - report it and I'll see if I can merged / move it where it needs to go. if they are just "look at me kicking ass" movies, they're staying in movies)

If they are "look at me I finished this instance, yay!" threads, they were moved into MMORPG - WoW.

....etc

As you mentioned, one thread PER BOSS for WotlK instances (Halls of Reflection and Violet hold I'll probably leave as one, because they are encounters as a whole, not really bosses).

Burning Crusade and Classis will get one thread per instance. All the old stuff (that is on topic) will be left there - but we're attempting to clean up forum and make it easy to find and discuss things. Cross-Boss posts (mixing threads) will be agressively purged. "lol I win" or "look at me" posts will also be purged.