Yeah the feedback you, @DeReel, and others provided over on storygames.com was invaluable. Good questions here.
We kept the rule that Harm from a group action only impacts the goblin in the lead. The reasoning is that it makes taking the lead on risky rolls feel more significant. Leading the party across that narrow chasm feels significant because most of the risk is on you.
We also found that allowing too many ways for you to get conditions on other players’ turns can feel rough: you are suffering consequences without getting to make an interesting choice.
However, in your cliff example, it’s still possible for multiple goblins to mark conditions. The lead goblin is the only one rolling for Harm, but another goblin can put their own conditions on the line as a twist. Maybe your goblin is leading but I tell you I might Panic. I get to pass you a die for the Twist. That way, there are multiple conditions on the line but there’s more clear buy-in from all the affected players.
I think your example of everyone putting dice in for a roll would likely increase handling time. I could see folks forgetting what each resolution point was. However, situations like the one you describe do come up: especially when someone makes Progress on an Action roll. For example: I’m trying to force my way through a door without breaking my urn. Another player says their goblin will cover me from the arrows and adds the Twist that they might be injured. If I make Progress on my Action, then I get through but the rest of the party is on the other side. So next the goblin with the mechanical arm tries (with the new Danger that their arm gets stuck) and another player offers the Twist that they might not be able to fit through, seperating themself from the party. Since the first goblin made progress on their action, this second roll is in a Good Position, making them very likely to succeed. Players get the shared stakes it sounds like your example was looking for, without too much confusion in passing dice back and forth.
Another way that having the acting player resolve all the dice really works is that it lets players get to have their own goblin take consequences to protect their friends. I three sessions at PAX Unplugged and in two of them, a player took a condition rather than letting a Twist happen that impacted someone else. Like: “I know how much that urn means to you; there’s no way am I letting it break.” Those are the kind of moments folks remember when it’s time to give new traits.