DCs for Individual vs Party Rolls

Continuing discussion on worker placement and dis/advantage math. Here's a thought, in the context of good old D&D Fifth Edition: for standard tasks, low DCs (~10) make more sense for rolls made by individual characters whereas, high DCs (~15) make more sense for rolls made by a group of characters or by a single specialized character.

This seems like the rationale behind the differing likelihoods of success in classic D&D using d20 or d6. The former die, used in combat, hovers around 50% for weaker monsters fought on-one-on and closer to 25% for stronger monsters that are fought by the whole party. The latter die on the other hand hovers between 17–33%, for tasks that can be attempted by up to three people at a time (e.g., opening doors).

I've noticed the same thing sort of happens in Fifth Edition. High DCs tend to be for tasks which require assistance or multiple tries to get right. For example, a target of 15 by itself has a chance of 30%, but that increases to 76% if four people are trying and only one needs to succeed. This is why, I think, it's a common DC for perception checks. High DCs for checks made by individuals don't make sense since the likelihood of success is so low. A target of 10 is fair for the average person, or 15 if the task requires someone skilled (in which case, it's virtually a target of ~10, just "targeted" towards a specialized character).

The real question: isn't this kind of trickery? Although the dynamics of these dice rolls are obvious if you think about it, the system comes across as pretending to be objective and impartial rather than specifically gunning for those outcomes (in the same way that Fourth Edition offers guidance to increase DCs as characters advance, so the likelihood of success remains the same even as characters' abilities improve). The coin flip remains undefeated in its transparency.