When recording vocals, I build a control center cue mix with the DAW output and the mic. To get the mic level in the cues high enough while keeping the input at a headroom-safe level I have to crank the phones volume knob to 100%, and I have to therefore be very careful to keep the DAW's cue mix level quite low.
I'm hoping that, in a future firmware update, you could significantly boost the level of the mic inputs into the in-device monitoring mix.