Atlas Mountains II is significantly harder than AM1 with the same reward.
Still if you need to include a 4th person you might consider doing it.
I can't find and up to date guide for AM2... it's rarely run.
If you want to give AM2 a shot (for fun or to include a 4th person), here is a picture of the
OLD AM2:
THIS PICTURE IS OLD! DO NOT FOLLOW THE ROUTES SHOWN!Click Image to Enlarge:
The new one isn't a lot different but there are some changes.
Most significantly Atlas is on the ledge. If I remember it right, the person listed as Position 2 in the picture will only have time to get Hyppolytus and then head to Atlas. That person will need to go around and use the stairs. Then person in Position 3 in the picture (I'm not confident that it is still position 3), will have to cover Adikia. Therefore this person should be your strongest.
Position 1 and Position 4 in the picture I believe haven't changed significantly.