There are two variants to play.. decide in front what version your party is playing.
Variant 1: The Portals
Phase 1:
Close the portals and kill the monsters.
Tip: You'll reach gold faster if every member closes a different portal and kills what comes out of it (no running with adds on you). After you kill you go for the next portal.
Phase 2:
Close the portals and kill the monsters.
Tip: Reaching gold is faster if one/two party member(s) close portals and bring adds to middle for others to kill. As soon as you shake aggro off of you, you go and close other portals and repeat. Classes with less DPS should be grouping adds in middle.
Phase 3:
Kill the boss and ignore everything else.
Variant 2: The Madness
In that skirmish, stand between the pillars to the opposite side of the entrance.
Phase 1:
Kill the monsters. You're slowly contaminated by madness.
You must reach one of the pillars in the 4 corners of the map to cleanse yourself.
Tip: At the beginning of the skirmish split into two groups, one always takes the two portals on the right and other group the ones on the left. No switching sides for less running and faster gold rank.
Phase 2:
Kill the monsters.
The pillars' energy slowly wears off, you will have to recharge it using the monsters' loot.
The more energy, the longer the pillar's effect will last.
You don't need to supply more than 2 pillars.
Tip: Same as Phase 1 tip except after 2 minutes time you switch sides to pick up the loot from the other side. Also a good idea is to charge pillars after you have picked up at least 10 loots from the ground.
Phase 3:
Kill the boss and ignore everything else.
However you will have to keep an eye on your madness.
When you're contaminated, you won't be able to use your daily skills anymore then your encounter skills. Run into a blue zone to heal. Beware, when a monster enters a pillar's area of effect, the pillar is disabled (the color changes).