You can do it in a party of 8 instead of 6.
Go to the Temple of Age (south of Divinity Coast)
Form a party of 8 there
Run South until you reach Sanctum Cay (really easy, 2 or 3 gates away)
Enjoy doing this Coop.Mission with 7 of your friends
nb: I know Temple of Ages is south of Divinity's Coast, but i did not manage to find a way to reach it from D.C. I found a way from Druids Ovelook instead.
nb: as you might have noticed, this trick let you jump right to the last mission before the Desert. It saves you from doing 3 or 4 missions I think