Believe it or not it was much easier this way. Although it took us quite a long time to finish the mission (probably around 2 hours!), we were never in too much danger.
We did this on the Jaya Bluffs version (we had tried Haiju Lagoon earlier with PUGs and by time we tried ourselves it had switched to Jaya Bluffs).
The henchies are only level 3, but as I'm sure you've noticed by now they duplicate themselves for this mission (so you have 4 henchies all level 3). They actually helped quite a bit. At times they served as one-hit speed bumps that let me close the necessary distance without taking a free hit; at other times the assassins (when the monsters were focused on me) did respectable poison damage (considering they are level 3's attacking level 28's!).
We brought non-sig rezes because there was a lot of dying; and I have to give credit to my friend he really made it all possible. Mesmers rule against Fingers of Chaos (as long as there is enough room to move around in, which means not in Tomb Ruins

We didn't get much (the advertised 50 orbs) but it was a fun challenge and I'm glad we did it.
Here are some pictures that show my skill deck, the henchies, and also the path we took in Jaya Bluffs!
Almost done! Just a group of 5 to finish off!
Final Result!