Most IEM have a highlighted treble to show off more detail, but not in the case of Atrio. It is not that Atrio doesn't have any detail, just not highlighted - which is why many people have commented its being not fatigue.
Using a speak set as analog, Atrio will be like having the sub-woofer directly in front of you while the tweeter at 10 feet away. Many other IEM will be like having the tweeter in front and the sub-woofer 10 feet (or more) away.
If you like Grado, that chance is you'll like more forward mid and a little sparkling on treble, something Atrio is not famous for. For your description, I think UM2 (or perhaps SE530) might be more fitting but it is more expensive. However, it is hard to be disappointed with Atrio - it might be different from what you are looking for, but it is still an excellent IEM for its price.