I dunno, I'm of the camp that believes it's better to go with a headphone where the technicalities match your preferences the most (as long as the frequency response isn't insanely different from what you like). Frequency response is easy to change, technicalities are not. My HD800's are EQ'd to flat bass down to 10Hz, a slight rising response to 1k (as recommended by Bob Katz for better midrange and vocal presence), a reduction in the dip from 2-5k, a reduction in the 6k spike (both through EQ and through mods to handle ringing and issues in the time domain), and a smooth upper treble response. It performs excellently with electronic, and I'd argue in many aspects is better than Audeze's offerings for many types of electronic music. I've spent time with the LCD-3, X, XC, and owned the 2's for some time (they were my primary headphones before I picked up the HD800's). I ended up being more satisfied with the HD800's with electronic music than any other headphone I have owned.
DnB is one of the genres where I would say the Audeze headphones have an advantage, because they mostly focus on bass and lower midrange, AKA the strengths of Audeze's headphones. However, despite the fact that my HD800's likely look a lot like LCD headphones in the bass and lower midrange, the technicalities are what set them apart and give Audeze the advantage. Audeze's headphones have a great amount of weight while still being decently fast, and parts of their midrange has some of the best euphonics I've ever heard. However, I've noticed that with the LCD-2's, electronic music was either amazing or disappointing. They have weight in the bass, but lack in energy, detail, and instrument separation when compared to the HD800's. They're also more selective with their texture. The bass has good texture (amazing weight, but it doesn't do as well with faster and more complex bass sections, it smooths them a bit), the range of brass instruments has amazing texture (the best I've heard), but the rest of it is very smooth (which is great for some music, but not so great with electronic music). I noticed I would listen to my LCD-2's at a much louder volume than normal to try to eak out some texture and excitement in a lot of electronic music. This actually led to a temporary reduction of my hearing range I was doing it so much (down to about 17-18k from 19.5k, thankfully it went back up to 19k after a bit). The HD800, in comparison, has very very good texture throughout the frequency range. The bass punches, the midrange bites, and the treble cuts (but in a good way). I'd put the HD800 at the top of the list for texture, which I personally consider very important for electronic. It even provides surprising amounts of texture at low volumes, so I never really feel the need to crank them.
Here's some examples of some songs I consider to be very good with Audeze's and with the HD800's.
Son Lux, I think is designed for Audeze's headphones. They sound absolutely incredible with a pair of LCD's. The use of deeper brass instruments seemed to hit my LCD-2's at the sweet spot of texture and their male vocals and heavy use of long decay fits into the euphonic midrange Audeze is so famous for perfectly.
I honestly wish I had a pair of Audezes still so I could hear the Undone single with them.
Now, the HD800's do very well with Son Lux, but not as well as Audezes.
For music that isn't characteristically dark like dnb and Son Lux, as well as music that excels in detail, complex layering, and texture the HD800's excel.
For example, The Flashbulb's The Bridgeport Run is my instrument separation and fast detail test song, and the HD800's are some of the best performers I've ever heard with this song.
The Flashbulb's Winter Map is also a good example of where the HD800 excels, smaller fast details. The "crunchy" type sounds used throughout the song are quiet, yet have a ton of detail and texture in them. It gets even more difficult when these songs are paired with heavy bass thumps midway into the song. Bleed and separation need to be extremely good for those thick bass notes to not impact the crunchy sounds and the HD800 performs incredibly well in this area. A big part of this is because of how excellent its transients are (especially at low volumes where many other headphones fall apart).
Yosi Horikawa's work is always very complex and textured, and use the entire frequency range. The HD800's are the easy winner with his work.
Of course, remember that these are youtube songs, so don't expect these to have the best quality. They're just for reference.
But also in general, I've found the HD800's to be more favorable with a wider range of electronic music because they're less picky in that series of genres. Their aggressive and fast nature lends them to make things sound more exciting, while the house Audeze sound lends itself to smoother sound, which can diminish a lot of (but far from all) electronic music.
And in the end, I wrote a damn wall of text. Apologies for making it so long, and if you got to the end, congratulations.
We definitely do, we lose upper frequencies as we age and as we accumulate minor hearing damage. However, it varies by person. For example, 17k tones are used to drive off kids under the age of 18, since most people above that age cannot hear them. However, there are some people in their thirties and even later that can still hear them.
I guess it is dependent on your perspective. The HD700's and the T1's are often considered some of the brightest higher-end headphones, and compared to them I can understand considering the HD800's laid back (frequency response-wise, not transient-wise).
I pair my HD800's with a Valhalla 2, but I also use a parametric EQ to make the bass more linear and the overall frequency response smoother (raise dips and reduce peaks). My setup is likely more "laid back" than yours because my bass doesn't roll off. I think the perspective is the biggest difference here. You're used to some fairly intense treble, so even though the HD800 is known for being decently bright, in comparison to what you're used to it is not.
But, I think it's important to define "laid back". Usually I think of it as a combination of a darker signature along with a slower rising transient and decay. In comparison to the T1 and HD700's, the HD800 does fit the bill in the first area, but not the second area. The HD800's rising transient and decay is very very quick, especially the decay.