This is probably the hardest one, but its not that difficult as long as you know what you're doing. Its also THE most straightforward.

 

Starting out, go north, kill the enemies, go east, PRESS AND HOLD the giant red switch which opens the east door, and continue. Kill enemies as you continue, and press and hold the next red switch. After thats pressed and the enemies are dead, continue south. Destroy the blocks that aren't even trying to aim at you, and continue west. Dispatch the Goronzoran dude, press both switches, and continue west.

 

Each person in the group must now pick a corner. Once everyone is on one, kill the 3 enemies  in your corner to bring down the barrier, then go north. Everyone must finish themselves, so there's no real way to help. Vol Dragon will spawn in the next area, so dispatch him quickly, then go north. Use the Sanctum telepad to continue on.

 

Area 2. Go north, kill the enemies in the area, then continue north. Press the switches in the specified order (Press N if you don't see them): 1st is right there in front of you, then proceed further north to the next. Go south from there, but not back to the previous area. Go west and north more for the next, then go straight east from there. Then go north west to the final and then to the next section.

 

Kill the block on top of the switch, and hold it down while either avoiding the lasers being shot at you. OR, kill them. Doesn't matter which. Proceed south, kill all the enemies that spawn, then west some more, killing more enemies and blocks.

After the door opens, proceed inside. Each person now needs to stand on a different switch. Once that's done, Caterdran will spawn North. After he is either dispatched or about 1 minute later, Caterdransa will spawn to the South. Similarly, another minute or after being dispatched, Quartz Dragon will spawn west.

 

If your group lacks good DPS, its best to send one person to hold off the other two until the first one is finished. Finish them in the same order they spawned, and be careful if all three are there are once. They will not be gentle with your body.

There is an easy trick to kill Quartz Dragon. Pull him behind the wall or behind a crevice. He will focus on trying to get to his target more than countering your attacks, because he is dumb. Use this to jump hit him constantly, and eventually he'll die.