Fort Mech Swarming Guide
Fort Mech is one of my favorite zones to swarm for two reasons, the first is it is extremely easy to swarm here and the second is it covers a huge level gap. You'll start off between levels 87 and 89 by swarming the large field of Fort Mech. This is seen in the first picture below. You'll want to avoid the red part of the map because the mobs over here are stupid hard. They have tons of HP and if I recall correctly some stun. The blue area is where you enter the zone and there are no mobs or mostly friendly mobs. There are a few non friendly but not enough to warrant going over there.
The main area to pull is the whole southern part of the map. The amount of mobs in this zone is just crazy. You'll be able to pull 100 or more mobs extremely easily, so bad you'll start lagging out the entire zone.
The area in red you avoid because the mobs have far too much HP and I commonly found a named over there that does a stun (though I think he can spawn in other places) both of which I mentioned before. You'll want to stay down here for quite awhile, at least until 91 I think. I stayed here until I got bored at which point I could easily handle the upper floors. You can always test the floor right above the ground floor if you get bored here and wonder if you can handle it further up. The mobs don't hit that much harder until you get to the very top.
Read further below for a strat on the upper floors and a key to this map.
You can go in and out of each building fairly safely, if mobs start cutting you off wait until the melee ones round the corner and kite them from one end of the building to the other then run out. Eventually so many mobs will agro you you'll start to lag the zone at which time you won't have to worry about them hitting you since they won't be where it shows them, they'll be 10 feet or so away.
Bottom Level (Light Blue): Start at the middle, pull the left side and stop at the end. Then go back to the middle and pull the right side before stopping at the end.
Second Level (Orange): Start from either the right or left side, pull the whole side and then stop at the end. Since a lot of these mobs are casters you will need to do a zig zag like pattern in the middle of the area to let some catch up or they will leash back to their spawn location. During this time I recommend dotting/nuking some of the gnomes to make it easier for a Mortal Coil proc later.
Third Level (Dark Blue): For this floor you will want to start in the far back rooms. You'll have to invis to get here but that isn't too big of a deal considering SKs get an instant AA invis (Gather Shadows). After you get back to each o the far rooms you'll wanna pull your train to the corner in the first room from the center of the top. Here you'll have a nice comfy corner to tank in.
That's really all there is to swarming in Fort Mech. As with all swarming, learning the zone comes with time!