If we have a small audio icon toggle in both dopsheet and preview then I think it is very usefull to hear audio when mixing things in preview.
Regarding the mixing values that we loose when exporting, I really think that it is a job of an animator to give a developer ready made track and mixing values as they were intended to be and let developers overwrite them if they need to do so. Here again, everything is painfully tested by animators in Spine but we loose the information on the way to developers. I mean if you are a small studio it is likely not a big deal bit once you grow you see that it is a real bottle neck or double work for the whole team.
