Good regions being painfully good is a paradox, ether the region is good or it is not good at all.
That is because you are going too far into the word. Remember this land isn't "Good" in the sense that it tries to do good things in the same way "Evil" Lands arn't evil at all just openly hostile (It would be like saying a Desert or Volcano is evil)
The idea of "Painfully good" is basically taking a concept that we would call "good" and taking it to its logical extreme or taking something good and applying it all the time even when it is not needed.
I mean havn't you heard the saying "That was so sweet my dentist could feel it" (admittingly I edited that because I couldn't spell a specific word)?
Possibly the best example I can think of for this concept is "Candyland" you would say that Candyland would be a great example of one way a Good land could look right? Have you ever thought of how hard it would be to survive in Candyland? Everything is made of Candy which while tasty gives little-no nutrician... The Water is drenched in sugar as well. You can't grow crops because the dirt is chocolate. Fires are pointless because the trees are Gingerbread. Plus since the animals are essentially immortal here eating them must be a horrific experience and give you terrible indigestion.
This is entirely without going into ways that this place could actively hurt you. Afterall a very common trait with "Good" locations in settings is how addictive they are or how they force you to join them.
So there you go. Candyland a good land being a horrifying death trap without ever crossing out of being "Good". It is just incompatable.
This is ignoring that so far "Good" as far as DF is concerned is closer to Whimsy...
But that is not good at all, that is insidiousness. If it were truly good then there would be no drawbacks.
Good is good, that is it. A good plan in not a plan destined for failure. A good church does not do questionable thing behind closed doors.
Having a good morning is enjoying a nice sunrise, a great meal, and friendly company. If you went to a good dinner, you would not have to look for tacks in you food.
If you rubbed a good magic lamp, the genie would be helpful and not trick you. I could go on and on but it will always be the same. Its not a trick question. Good is good.
Of course when I say good I mean good as seen by dwarfs. A good region would have all the things that a dwarf would want to have at a site.
The region is good because of its high compatibility with the dwarfs. Dwarfs call them good for a reason.
While I understand the 'too good to be true' line of thought, there is no need to make the regions needlessly obtuse.
If you want to introduce more region types into the game, more power to you. But there is no reason to alter the definition of good to fit your desire.
Besides there are plenty of good regions in the history of fantasies. Whether or not the regions stayed good is another question, but that is another kettle of fish entirely.