Lightfoal and myself, Pelmen Silverwolf, would like to present to you our farming guide for what we affectionately refer to as "The Trio". Namely 3 bosses in arborstone in a single, 8-12 minute run

My apologies for any errors in this as I've never tried to include pics with a guide before.. heh
Who you're killing
Craw Stonereap
Zarnas Stonewrath
Meril Stonereaver
What you need
A Monk/Mesmer or Mesmer/Monk combo works the best here. Ranger/Mesmer might work, but the cast time on troll ungent is a bit slow and it makes getting through the first part much, much harder.
9 points in Illusion and Domination, 8 in Inspiration, 12 in healing. Feel free to tweak as needed, the +8 healing breeze is very useful though.
Skill wise you'll need this setup
skills.jpg
The skills from left to right are Illusion of Haste, Backfire, Images of Remorse, Spirit of Failure, Empathy, Spirit Shackles, Energy Burn, Healing Breeze.
Armor wise I have standard droknars stuff, though I do have a +20% enchant staff that helps a little bit. A longbow is also needed for pulling.
If you're a really bad runner, having more Luxon favour than Kurzick helps a lot as you'll spawn at a rez shrine that's usually easy to get to the bosses from. However, there's sometimes a warden patrol sitting on it, so this isn't recommended as a run strategy.
The Run
Head to Altrumm Ruins and exit into Arborstone. Hug the left wall, go through the arch and keep hugging the wall as you advance. You'll pass a group of wardens without aggroing them and head up a slope into a narrow, very high ceiling hall with a group of wardens blocking the path.
compass1.jpg
Edge up to them, hit healing breeze, then wade into the mess. As you pass through them you'll usually hit a spiked trap, crippling you. At this point hit illusion of haste and run like heck up the hallway, kiting side to side to avoid any arrows. If you're close to dying, stop and hit healing breeze, you can always use illusion again and keep running. Once you've lost aggro, move back to a doorway you passed. Just beyond it is Craw Stonereap. What you want to do is aggro Craw and then get back out into the hallway so his wand attacks are hitting the wall and not you. If you back up far enough, he'll edge closer to the wall so you can get him in spell range.
craw1.jpg
Once he's there, start out with spirit of failure, empathy, backfire and images of remorse. Keep these on him at all times and let you health edge down to about 100. By this point he'll have started to cast various necro hexes at you and will be sacrificing health using them in addition to taking damage from backfire and empathy. He'll drop in a minute or so.. really a no brainer.
Now advance past Craw a bit and you'll see target number two.. Zarnas Stonewrath. Zarnas is a bit different, but the strategy is very close to the same. Get out a bow and pull him so the corner of the wall is between you and his stone dagger spamming. It's advisable to use healing breeze before you try because those daggers can hurt! Remember, kite for damage reduction.
zarnas1.jpg
Once you have him positioned, wait for him to use gale then try to cast backfire. Chances are he'll just smack you with gale again, but he seems to run out of energy to cast it after a while, so just be patient and keep trying. Hit him with images of remorse while backfire is recharging to overcome his natural regen, and energy burn if you have the energy available. As he slowly dies it'll get a bit trickier. Close to the end he'll stop casting and swap to melee, so you'll have to time your spells carefully. When he's close to dead hit empathy (longer duration) followed by Backfire. This should almost kill him, and when he's at a sliver of health hit energy burn, and he'll drop. This timing takes a bit of practice and can be frustrating, but it's completely doable. He won't suicide just from backfire, so if you have to, recast backfire as soon as it comes up, then hit empathy again right away and keep trying. At worse, let your energy come back up and try it again.
Once he's dead grab your goodies and advance along the path, looking for a single red dot on the right. This is Meril Stoneweaver. Again, you'll have to get a wall in between you and him, but it's not so hard. Move down the staircase by him just a bit, and peg him with an arrow, then back up so the corner is blocking his fire.
meril.jpg
Now comes the fun part. Killing Meril is all about energy denial, so start off by casting images of remorse. He'll almost instantly shatter it, so hit spirit shackles followed by energy burn followed by spirit of failure. This is the choice order to do it in as it drains his energy the quickest. Hit empathy followed by images of remorse, and then start cycling through the skills as they recharge. You can stop using energy burn when it reads as 0 damage. Meril may shatter a few more times, and might even sneak in a shield of regeneration, but between spirit shackles and spirit of failure your energy will be at a constant level and his will rapidly drop to 0. Keep spamming empathy, shackles, failure and remorse as they recharge until he dies.
Congratulations!