Echoing what others have said that a DME is not used as a live mixer.
I do a bit of live sound, the most I need for the size of things I do is a Driverack. I have some friends that have done hig end tours, and others that work at large venues. My venue/theater friends are the ones using DMEs. They have a board and it provides one feed to the DME, the others feeds would be a lobby paging mic, Muszack feeds, etc. the outputs would be the flown speakers, the subs installed under the stage, under balcony feeds, e tra subs when doing heavy acts, the lobby speakers.
Also some small control panel that allows simple changes/scenes. One the speaker feeds inside seating area you would configure parametric EQ to correct for speaker issues, delays so the sound from the under balcony lines up time wise with the mains. Sum the L+R for the lobby feed., etc.
Software on a PC allows you to layout all the blocks of funtiona you want, and then it generate a file that downloads into the DME.
Anymore, you put a Dante card in the DME and then all the audio stays digital from the mixer, no extra conversions and the added delay.
In case anyone wonders about delay and latency, it can be a real killer to players. It gets worse when using in ear monitors. Having bounded latency is a must. A few milliseconds changes the groove of a song.