I can see exactly where you get this from, however, if you increase the attack value of avian/dwarf to 8 (relative strength based on next age/-1 from orc/UD) you would find that the UD have not been weakened, avian/dwarf have been strengthened in comparison. I would concede that the UD/orc nerfs should be weakened a little in response to the other races getting stronger though, or weaken the buffs on avian/dwarf thievery/magic respectively.