Actually, I find the combat doctrines too limited. I championned for a more detailed system in which you could establish a priority order for each of your groups, but to no avail.
I don't know if you tried the expansions, but they add a lot of variety and uncertainty to the base game (as you now need to find out what Empire Advantage the opponent has, and which alien techs he may have found).
Anyway, the expansion is almost upon us (updated to: art in art and final development).