For the betrayer scene finish the quest with Ripsnarl, at the end you got a treasure map, you can loot the skull of Guldan in a chest near the lac where the Orc was against a pole (if you have finished Jaina quest.)
If you got it, go to the port and jump directly in the water at your left, swim and after you join the little beach, continue in this way, you should find a little path. (At this moment, you need the 1st ability, you need to burn ivy).
After reach this, you must see an altar, use the skull of Guldan near it.
For DK scene i search the last step ..