Ok, let's get back to looking at the facts, rather than unsubstantiated fears...
Above, you see the FR of the top Sennheiser and Beyer cans. In the midband, all of them spend a lot of time at +5dB. This is really where your ear will set the reference point. From that +5dB reference level, the HD800 is down -10 to -12dB at 2kHz. At around 6kHz, there's a sparkle peak in the HD800 followed by gradual roll off, which actually looks pretty good, at 20kHz, being only -13dB below reference level.
On the bass end, the HD800 is about -8dB below reference at 10Hz, which is also quite good. The traces for the other cans are there for your reference and you can compare them to the HD800.
Looking at the FR chart posted by PA above, we can see the reference level is set appropriately at 90dB, and drops about 10dB to 80dB around 2kHz. There's another dip around 4kHz to -12.5dB below reference and then back up to the -10dB below reference level with a peak around 12.5kHz of 2dB below reference level. At 20kHz the can is 10dB below reference level.
In reality, any measurements above 10kHz are suspect for any can on any dummy head due to un predictable standing wave and reflections inside the mannequin era canal, head and headphone cavity.
Looking at the bottom end, the LCD-2 is flat at reference level from midband to below 10hZ.
This does not say "dark" any more than any of the other cans shown say "dark." You really need to listen for yourself before you form an opinion.