That's good. I notice that D&D has a breakdown of what DCs should be in five-point increments, which is much better than stressing over the difference between a 13 or a 14. Still, I find it odd that DMs have to ask themselves "is there a roll needed here?" or "would a roll for this auto-succeed?" I prefer just to let PCs tell their share of the story, and when it occurs to me that MY version of the story (as GM) would be different from what I'm hearing, that's when I ask for a roll. It's a subtle difference, but a difference nonetheless.
There's an interesting aspect of D&D difficulty classes: they're the exact same thing, mathematically, as penalties to a PC's roll. In a sense, EVERY DC is 10, and when things get more difficult, the PC's roll just takes a penalty against that 10. So I don't see PCs as having different DCs to accomplish the same task. Your return on the investment of customizing DCs is that you have a custom-tailored DC waiting for a PC who might not even end up rolling for that DC. Wasted time. If you use one DC, and just apply a bonus or penalty to the PC's check who is making the attempt, then at least you're spending rules-related time on a character who is invested in that rule/judgment/DC.
You stopped a little short of a product endorsement there, but I'll take it. I would hope that the players in that situation understand the DM's interpretations, otherwise they're headed for GM and system failure.