Got Mimiron's Head today. I decided to have some fun with it.

As a hunter I've been able to do it solo in 10 and 25.

What i do is put my pet on passive in the arena and kill all the Captured guys who start the event except 1. I then kill him near the door switch to the gauntlet and begin opening it right away. After that I need to get down the hall and aggro the first mini-boss guy and run back to the arena as quick as possible before the ball of lightning comes down the hall; I do this with the Post-haste talent, rocket boots and when I slow the aggrod NPC's down with Frost Trap then Aspect of Cheetah.

Once I'm safely in the arena the Giant is still on me, I DO NOT kill him! Once the ball of lightning fades I run back over to the still open gate but from the other side. A few seconds later the whole place resets and the Captured Alliance or Horde are back in the arena. I then take the mini-boss to his door and kill him and any other NPC guards.

After that I run up the stairs and kill the 2nd one opening the final boss leading to Thorim's chamber. Now I go about halfway down the hall and stop, this is where my pet comes in. Now I use my passive pet to start killing the Captured guards to star the event again. I do this by typing target commands like:/tar Captured and telling the pet to attack them one-by-one.

After the last one falls Thorim does his little speech about remembering you, but don't charge him yet. Wait until Sef appears to tell him we're tricking him, whenever I charge too early he totally resets. After you charge him you know it will work when he says the line "You dare attack me at...blahblah"; after that you are free to jump in the arena and kill him as normal.

This should work with any class with a controllable pet, but I've seen guides for other classes so there is probably several strategies.