My issue is not with the GMs who actually use judgement to decide when you can and cannot take 10. My issue is with the people who say "It is a long way down, so no take 10 for you." Or "No take 10 for sneaking past the dragon because dragons are dangerous." In other words people who use GM's discretion to effectively ban take 10 because
So you have an issue with the rules then, because sneaking past a dragon is as in immediate danger as it gets.
And with the design team, because thats the exact sort of thing they called out as grounds for the DM to require rolling.
And people that listen to one or the other.
I don't think arbitrary means what you think it does.
I strongly disagree with your dragon example. For me it is exactly the example of a situation where you can take 10, and, for me, the developers post I have read support my position.
You are in immediate danger? No, the dragon isn't attacking, nor searching for someone.
Failure is dangerous, so you can't take 20, but you can easily take 10.
BTW, dragons have blindsense,60'; so the whole argument is moot if you are at less than 61'.