yeah, i mean, maybe i seem like a newbie, but I totally don't get what you're doing here.
I've always thought the signal chain as
instruments > mics > preamps > soundcard > PC(DAW)
and for monitoring. my soundcard has outs > headphone amp.
in your case
" in: 16 mics > analog mixer > protools le + additional interface > DAW
out: DAW > protools le + additional interface > analog mixer > headphone cues, monitors etc "
from mics > analog mixer (you're using as a preamp or/and you EQ the recording inputs?) > pro tools etc etc
out: DAW > pro tools > analog mixer (again? unless you want the band members to mix at their own comfort?) > monitors.
i'm not sure if this is what you want, i'm selling this echo audio layla 24 is it of any use? it's got ADAT in / out / midi / 8 analog ins and 8 analog outs.
http://img133.imageshack.us/my.php?image=echoaudiolayla24pci02gy5.jpg
how I had it connected was.
Audix Fusion 7 mics > 2 Behringer ADA8000s > echo audio layla 24
1 behringer adat is connected by an optical light pipe.
1 behringer adat is connected by 8 XLR > TRS 1/4 jack
that's 16 recording tracks.
hope this helps.
20¢ worth.