You guys certainly do sound like HE-400 apologists, especially when claims that the HE-400 is as good as the LCD-2 are thrown around.
I'm convinced the HE-400 is a good, but flawed headphone. Vocals disappear behind the drums, hi-hats, and instruments when they clearly shouldn't. Sibilance is a frequent problem and treble balance is also an issue. The "thinness" of the overall sound is also a negative. Plus, the lack of decent bass impact with velours and a less-than-ideal subbass extension.
In the end the HE-400 is very technically adept but I don't think I can call it "musical". It doesn't make the music fun and engaging the way my D2000s did, for instance (and I'm sure there's a multitude of headphones that can be described as more musical in or around this price range).
I was with you on the "sometimes sibilant" but you lost me on the lack of Bass. I had a set of HE400s and they were anything but "bass light". Quite the opposite for me. I thought they had fantastic Bass /shrug.