----- EDIT THIS DIDN'T WORK AT ALL ----- It just happened to sound fine on the first synth I tried it on, other sources sound absolute trash.
I have found a temporary solution. I don't know if maybe everyone already knows this and if there is something with doing it this way that is not good, if so please let me know.
Go to audio/midi setup and go to your aggregate device, you can check a box all the way to the right of each "slave"-device called drift correction. If I understand correctly, it's software doing the wordclock cables work.
I just happened upon this, so again, if there's something wrong with this procedure, let me know, I just needed to share this as soon as possible since I know you are going mad with this problem just like me...
----- EDIT THIS DIDN'T WORK AT ALL -----