He's soloable as an SK as well, you just have to be quick about it to avoid that 7k DD. I basically have to chain tap him, so have 2-3 taps up for safety.
He has to be relatively close to cast snap on you, so if you're kiting and want to avoid taking ~6k damage every 30 seconds or so stay far away from him.
Spawned for me in the bay west of Jardel's Hook - actually two Tetratons popped at the same time, so it mostly does not have a specific PH but can spawn from any sea turtle in that area.
Confirmation, and a few notes. From what I've seen while doing the Snake Milk task, he has about a 5% chance to spawn from any given sea turtle in the west bay. That may sound low, but there's 10 or 11 of them in various places throughout the area. It's hard to see in the water though and their depths vary a lot, so many people may be missing a lot of PHs. These are also the PHs for ringed sea snake, which seems to spawn about 10 or 15%. I've seen 3 Tetratons up at once in close proximity. Makes for some interesting pulls. He has decent magic resistance, resisted the first 3 -60 resist slows I threw at him. Later on, after I'd retrieved my lungs and spleen back from his droppings, I decided to try another method. I pulled with Putrid Decay (disease resist debuff) and used Virulent Paralysis (disease based AA root). It lasted the full duration and let me keep my internal organs this time. I've killed 5 Tetratons, needing 2 VP's each, and it has never broke. So his disease resist is pretty bad. The aug is unfortunately his rare drop, as I've gotten the ring all 5 times. He tries to run at low health.
On a "stupid trivia" matter, Tetra means 4, and of course ton means 2,000 pounds. So his name is apparently referring to his weight: a Roseanne Barr-esque 8,000 pounds.