It's interesting to read about the he-400's being overhyped, especially given that they are an entry-level planar targeted at mainstream listeners using budget gear & lossy tracks. For that demographic, they are pretty solid - and introduce a new audience to the HiFiMan brand, if not planar-magnetic technology. Look... the HE-400's can't compete against flagships, they don't feature stellar technicalities, and they won't scale well with better gear.
But they don't have to do those things; that's not their intent.
Related: It's difficult to set expectations on a $399 pair of planar magnetic headphones.
Uh, well, the HE-400 measures <FAR> better than any consumer grade headphone I've ever seen. Really good attack and decay, good square waves, excellent bass extension, good treble, nice flat response, AND its able to be driven by almost anything. Save for high THD, it's really damn solid. I'd say the HE-300 is more of what you described.