After doing some more browsing in the forum this seems to be really common problem for people and that there are only 3rd party work-around to this and that is only for windows. How can it be? I bought RME because I wanted quality and I'm in general really satisfied with the product(sound and drivers) but the whole user experience is crippled because of this weird detail in TotalMix. So please somebody let me know if there is some solution to this.
I quote another thread regarding this matter. It pretty much summarizes the whole thing:
And as many others, first that i have noticed, that the Volume Control in Windows is not controlling TotalMix FX MAIN OUT fader.
Have searched this forum - some bizzare third party app hacks via MIDI for this feature, some of them are not working anymore, some of them partially working.
Many-many-many user requests dated from 2010 year to make this option native in TotalMix FX - and total ignore from the RME software developers (requests on not to make it as default feature, but just an ability to turn it ON for those who really need it).
As an owner of this Premium product i totally did not understand this company politics - ignoring the mostly popular request.
Many users are using the RME sound cards not just in studios but in couple - home studio/desktop computer connected to some theater and etc, so they really do need an option to have this linking (Windows Volume Control - TM FX MAIN OUT).
And I apologize if this is because of my error but I've been trying to figure this thing out for hours. And I think it shouldn't be like that, after all it's just about being able to control TM's main with Macbook(or windows') volume controls(not just the channels 7/8!). You would expect to have that after spending almost 900 euros to audio interface.
I'm grateful for any replies or help with this matter. And again apologize if it just me being dumb 
Thank you.
