WOOT - SUCCESS!!! After my last foray into the Underbog I actually returned a second time yesterday and died probably a dozen times trying the get past the naga sentries. I was pulling out all the stops, I had a sprint/evasion macro and a cloak of shadows/vanish macro that I would hit in close succession. You'd think this would get you through pretty much anything, but the naga patrols were hitting me with a bleed effect that was breaking my vanish every time.
So I was pretty frustrated and started a thread on RogueSpot to get some input from other rogues. One guy mentioned that he stood in front the sentries and did the sprint/evade and had no trouble. I realized that by sneaking up with the patrol (in the hopes that they were providing cover, lol) I was probably hampering my own efforts. So I tried waiting until the pat was at the bottom of the ramp and then I walked through the sentries at the top. Bingo! I was able to sprint/evade through them without attracting the pat. The key is to not hit vanish until you get around the corner and to the bottom of the next ramp. That way you are out of their aggro radius when you vanish, otherwise they keep chasing and hitting you, breaking the vanish.
So bear in mind that the myrmidons (patrol nagas) hit you with a bleed effect that will negate your vanish. Make sure you stay out of their melee range as you sprint by, there's another set on the other side of the sentry nagas. Also it's probably a good idea to use cloak of shadows here with vanish since there's are some casters that could nail you with a dot. I saw mostly fireballs, but you never know.
Once past there is a chest spawn under the ramp, but I would go up the ramp to make sure you've lost your followers. There's a group of 4 pathers around the ramp chest on a very short path. At level 67 I was able to stand behind the chest at max range, wait until they pathed out and quickly click, open and loot, then scoot back and stealth before they got back into aggro range. This same chest also seems to spawn in the corridor with the fen rays and bees (right before the hunter boss), and I was not able to loot it at 67 without pulling aggro from the rays. There's probably a 3rd location but I only did 2 runs of this area of the dungeon so I didn't find a 3rd spawn.
There's an adamantite node in the same corridor with the fen rays, but closer to the stealthed NPC and can be mined without aggro (at 67 that is). The other adamantite node in the front of the dungeon has several locations. One is in the water with the fishies. They can see stealth so I haven't tried to get that one. Another is at the front of the ramp to Hungarfen, and a 3rd is behind the same ramp near the water's edge. Both of those can be mined if you are careful. I think I also had it pop once along the closer wall where the sporebat/elementals hang out, but that's a rarer spot. It's usually one of the two spawns by the ramp.
There's a chest spawn that's along the back wall behind the ramp. Not near the water, but you follow the curve almost where it opens back out into the cave. You can easily avoid the pat back there and get that chest. A buddy told me the chest can also spawn at the top of the ramp that leads to Hungarfen, but I don't think I've gotten that one yet. The last spawn is past Hungarfen on the next platform, right next to the Bog Lord. I'm able to loot it at max range, but someone lower than 67 might not be able to. I'm really close to him when I do it :)
Once you collect the first ore and chest you can head to the next ramp and do the sprint/evade + cloak/vanish trick if you want to keep going for chest #2 and ore #2. Otherwise just walk out and reset. I can do the first part in about 5 minutes, it takes about 10 if you add part 2. The nice thing about doing the whole dungeon is that you can walk right out past the Black Stalker and exit at the entrance to easily reset and go back in.
Most of the ore nodes will be regular adamantite, with maybe 20-30% chance of a rich vein. The chests drop about 5g in cash, plus a level 64 green item. There will also be either some potions or scrolls and twice today I got an uncut gem. So the loot is pretty good, even if you just farm the first section. If you need to farm Sporeggar rep you can also grab the hibiscus that are scattered about.
Good luck and feel free to share any other tactics you might discover during your runs through the Underbog :)
***For those of you new to my blog, I have other articles on stealth farming here***