Directions as follows : standing with the Teleport pad behind you, go forward to the right - you will see you're at a sort of station platform, follow the passage on your left, staying on the left hand side platform, killing troggs as you go, you should be able to take them one at a time. You will arrive at the instance portal, go through it. Continue along the passage, and you will see a large chamber (the hall of gears) in front of you. Pick off the troggs where the passageway opens out into the chamber, and a couple to the left of you as you turn onto the high level shelf upon which you stand. Look over the edge you will see a large gear below you set at an angle. Jump down onto it, you should be safe if you land in the middle of it. I think I took something in the region of around 1000 damage on this jump but its nearer 1600 if you drop straight to the floor. There will be slimes and elementals patrolling the floor below you. Viscous Fallout is amongst them. When you've recovered you can pick the right moment to pick your spot, jump off the cog and go kill him. Running to the wall is usually the safest spot so you don't have to watch your back. When your done, the easiest thing to do is to hearthstone out to Booty Bay and TP in again later on if you need to run it again (30 minute instance reset I think ?), although you can fight your way up through the 'dormitory' and 'clean zone' to regain the upper level and back out the way you came. I've been running this instance many times for the hydrocane with no luck so far. Good luck !
Edit: Finally dropped after 24 runs:
16 Acidic Walkers
7 Toxic Revengers
1 Hydrocane :)