Ok time for a little update. After a lot of experimenting, and to the surprise of probably nobody but myself, my ER2XR aren't faulty, Etymotics are just massively darker than what I had anticipated. That's what reading reviews of audio gear on the Internet gives you, I guess...

Nothing an EQ can't fix though, so I tried oratory1990's USOUND1V1 EQ preset with promising results, despite the USOUND1V1 target throwing the Etymotics' tonality out the window. What really did it for me was the 8kHz boost, although 5dB just wasn't enough for my taste, so here's what I settled on for now:

Preamp: -7.2 dB
Filter 1: ON PK Fc 8000 Hz Gain 7.5 dB Q 1.000
Filter 2: ON PK Fc 11000 Hz Gain -5.0 dB Q 5.000

What it looks like. Usual disclaimer, this is what I like, for the music I listen to, and may not suit anybody but me. However I can finally listen to music without feeling the need to push the volume to unreasonable levels just to hear some treble. The Etymotics now sound great to me too! I can finally understand where the praise comes from, and just witnessed myself bobbing my head to some music while writing this.

Huge thank you to everyone who took the time to help! You saved the Etymotics for me. I might give the tuning kit a try in the future, but for now I'm perfectly happy with this simple EQ profile. Cheers!