My ears are getting older year by year and hour by hour, so any brightness issues have apparently resolved themselves. The high end doesn’t bother me at all. But, I’ve not tried super aggressive content yet. I dreaded using ANC on the APP1, as it sounded like listening through a paper bag on a stage as narrow as the HD 600’s. It was akin to mono with more space.
With older ears, maybe I should borrow @pennstac’s Grados now. 
I nursed my dying APP1 batteries along because I knew this was on the way. I’m amazed at how good the noise canceling has become. Fans and clothes dryers just disappear. Loud traffic and trains are cut down a lot.
One thing I did not expect is that APP3 results in streaming tracks switching over much faster when using my Apple Watch. With the APP1 there were long delays before music started, and often a 5-10 second handshake between each track. That disappeared with the APP3. Weak batteries? Hmmm?
The excessive bass does bug me on warm tracks.
EDIT: I found this site with info on how to use iPhone hearing accommodations as a sort of EQ. Testing now. It does change the profile (I boosted the “vocal range” to “moderate” or “strong”).