Chiming in again. Again, not disputing the math.
Let me see if I have this right. And, please, type slowly when you correct me, because I'm innumerate.
We have a system that gives a range of success chances. At one end, you have a group that pretty much tries to go it alone, prima donna style, takes no advantages and winds up with a very low chance of success (25%?). On the other end, we have a group that works like a well oiled machine, takes every possible advantage and winds up with an almost guaranteed chance of success (100%, possibly more).
Is this really a bug? Isn't this a feature? You have a system designed specifically to reward cooperative play. If you want to succeed, you need to work together as a group (Aid Another, taking actions that don't contribute to Success/Fail but give bonuses to others) and your chances of success dramatically increase if you choose to work as a group.
Additionally, it seems to me that many of the bonuses - rituals, Aid Another etc. are mostly under the control of the players, not the DM. So, it's up to the players to come together, work as a group and solve skill challenges.
What am I missing?