I wholly recommend adding bread spice to your rye breads. Gives a nice complexity to the flavour profile.
I use equal parts cumin, fennel, coriander and anise seeds, coarsely ground. 10g total per kg bread.
mixed flour, hmm? I always do 100% wholemeal rye.
Once when I ran out of rye, I used 50% fermented/leavened rye, 50% wheat (I don't remember the kind), and the result was of "edible" category. Dry and weird.
What's your trick to make it good?