I just recently got an hybrid MK3 second hand. It is getting hot, apparently normal, after some hours of use, but probably didn’t help that I put it just so close to the part of the laptop that frees up the heat from inside (fan?) Something to watch out next time 
In any case, I tried duplicating the main out and routed it to the headphones out with no troubles, just using the menu from the front panel of the sound card, and I guess any other channel or channels can also be routed in the same way… I need testing more options but so far it’s been a massive improve in sound quality for me. So far, can be any happier. I also test it as external mixer without computer and I was also pretty impressed.
Great device that needs a good read and test on the manual. Looking forward to discover more stuff and try the different software and effects that includes with it. Apparently reverb, eq and compressor are pretty good.