Sartharion the Onyx Guardian, the 10 (and 25) man encounter underneath Wyrmrest Accord, has two ways to the encounter.
The easy way to do it is to kill the 3 minibosses in the zone before you encounter him. This trivializes the encounter.
The hard way is to kill all of the trash, but leave the minibosses up. This causes the minibosses to become part of the encounter when you engage Sartharion. This makes the fight significantly more challenging, has scripted events, and other such goodies.
Basically, it goes from making the fight an absolute pushover to something very, very challenging, well worthy of being done by the 'hardcore'.
We started learning it yesterday, came back today, and killed the 10 man version this way. Bonus loot dropped!
We're going to try the 25 man when we can manage a raid for it.
Went in with Vis Maior helping fill out the raid, and just did the 25 man version of this as well, all 3 drakes up upon engage, etc. It's not nearly as well-tuned or hard as the 10 man one. Had a dev there watching so they're already aware and are going to be retuning it appropriately.