Animal has already taken a swipe at the 164 DC, but I'd actually say that the DC at 100 feet is worse. I mean, I can spot just about anything at 100 feet on a plain, and I'm nearsighted and not an adventurer/hero. But our PCs have to make a DC 30 check to spot minotaurs at 100 feet on open land? That's preposterous.
(Note that I'm not calling you or any member preposterous. I'm calling the rule preposterous if it is in fact in RAW.)
(Note also that the rolls are just to notice the other party, so it's not like the DC 30 is to spot them in hiding or something. This is a "Nobody is aware of anyone else around, so they're just going about their business" scenario. And it takes a 30 to see that at 100 feet? Bizarre.)