I'm not truly positive that the minimum gain is actually +28 dB from front end to ADC. A lot of speculation when this recorder was first released was based on it being totally unusable in concert recording applications based on that number.
In really loud situations I run MIC in on low and have to crank the gain knobs to 50 - 75% to get usable levels (for me between -12 and -6dB) with my Schoeps MK41 that are 16 mV/Pa - so about the same as your Avantones.
If the machine actually adds +28dB at the minimum gain settings (LOW, knobs turned all the way down) it would be way too sensitive at concert volume but that's not my experience at all. Even if it does, which I doubt, my Grace V3 added ~25 dB of fixed gain to the analog outputs no matter what the settings and I often ran the gain knobs higher than zero even on loud sources.
I guess I've been lucky and not had any issues other than the same early power loss probs that were finally resolved.
Maybe I can figure out what the minimum gain on each setting truly is by sending a regulated test tone somehow.