Leeeeeeeeeeeeeroy...?

Simple explanation:
Clear up to and including Kyrak.
Don't leave the room.
TIP 1: Resurrect Leeroy and as soon as he is alive you can leave him and begin trash, effectively adding 70s to 900s timer.

Kill every mob up to and including the arena boss.
Kill every mob up to and including the Son of the Beast, including two ogre guards near door to bridge of Ragewing area.
(Stun/CC/Grip the ogre casters that try to open the cages - will greatly speed you up)
Son of the Beast is not marked on the dungeon map, but he is before Ragewing.

TIP 2: If you have low DPS and need to engage Son of the Beast as Leeroy is running to you, drag beast to opposite corner and stack in that area so that as Leeroy runs in, he will not run through fire trails; he will move to where the Son of Beast was standing originally, and he will wait there safely until you kill the beast to run over and loot his shoulders. This also gave our low ilvl group lots of extra time as the beast was 50% hp when Leeroy got to that room.

After he loots the beast, he will automatically become your follower.

And magically levels from 60 to 100!

I tried soloing this as a lvl 110 warlock. I was hoping I'd be able to resurrect him with soulstone (combat res), but sadly it doesn't work. Seems it has to be a proper res.

If your class doesn't have a regular res, try to find someone that'll join you.

The video which made him & his yell famous: https://www.youtube.com/watch?v=LkCNJRfSZBU

I hope Ben Schulz, who played Leeroy, will get to record a few lines for his ingame character.