GMM has the best non-visible armor and weapons in the group game. The mobs in the missions are easier than the mobs in the open zones. The mobs in the missions are 108 -110 except for the names. The problem is the mobs tend to be clustered in one spot. The ranger was too low to CC mobs so I did all of the pulling on my BST. My Group geared BST already has the GMM pet earring, but even a lower EM pet can tank 1-2 of these mobs.
In the Darkness Howls mission, when you first come in there is a single mob at the bottom of the trail. He is usually standing there, but if you wait long enough he will path there and make for an easy single pull. The next pack has 3 mobs. I back the Ranger out of the way and cycle through the 3 targets to find the DB one instead of the even cons.
I pick the DB one because I am about to use the mother of all BST splitting tools... "Flash of Light"! It doesn't always land so you have to give it a couple tries, but eventually you can get down to 1 to 2 mobs alone which I sick my pet on and start DPSing on the ranger while I wait for aggro to clear on the 3rd mob. After that, everything in that first section is a 2 pull which your pet can handle.
I am typically trying to get exp, so I divert from the normal flow of the mission and go under/out the front gate and clear all the mobs in this section. If you are careful, every pull is 1-2 mobs.
The second part of the mission has 8/9 mobs all together on a platform with a shack on the hillside. I typically setup way up the hillside (Thanks Cinnabee for this tip) and have my ranger invis'ed. I once again hit one of the mobs with FoL and run up the hill and then FD when 1 to 2 mobs get in range. Put the pet on them and wait for aggro to clear and then rinse and repeat. The problem with this method is sometimes a pack of 4-5 will warp on top of you and then it goes down hill from there.
The third part of the mission has you pulling mobs out of a cave. The mobs will path to the front of the cave where you can easily pull them from outside with your back to the wall. The problem is there can be a stack of 3-4 mobs at the front of the cave. As long as you keep pulls down to 2 to 3 mobs you should be fine. Once you clear 10 then you get to the next stage of the mission.
The fourth part of the mission has you on the platform by the supply room pulling out mobs. Take your time and keep pulls at 2 mobs and you will be fine. After you you finish this stage you will get an emote if the named spawns. It is pretty rare.
For the last part of the mission you go out/under the main gate and if you cleared this area previously, the only mobs that will be up now are the target Howler mobs and the PHs for the named mob. I think you have to kill 5 howler mobs and then you get to open the chest. Howlers are the only mobs that see through invis.
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