This is one tough zone to crack. Once you zone in your in a small building. If you walk out of the door and to the right is the zone out. If you invis you can run straight to another open building wait and out straight to another. Once in the third open building you can sneak up the path. As I have found the only 2 mobs that see through invis are the Golems and Shissars and they roam the areas. Most of the time if fighting a Golem or Shissar the snakes and beetles will not aggro but it has happened from time to time. Once you fight a snake or beetle they will help each other. The little beetles are the worst because they come in 3's most of the time and are hard to hit and see. I have done this solo and this is how I did it. I snuck through to the pathway and killed a shissar there. I used that path to kill the insects there. You might also want to get the Adapting to the Environment II also since you need to kill snakes and gorillas. Alot of zoning in and out when your trained by 4-6 mobs but it can be done. I will say it is a hit or miss when you zone in the a Shissar isnt standing in the doorway to the open building. I did this with a T5 merc and Im level 85. If you do get a group it will go faster though. The center pathway has 1 gorilla that comes out but you can take care of him quickly with no aggro to other mobs. The right path goes to a river and I stopped before going any further since I got trained with 7 mobs and ran to the zone. So I would call this zone a hit and move type. The longer your fighting or standing still the more chance of getting trained.
Herachilles 85

