This.
Only way I see a Dwarf/Rogue being good is if you're using them to have a Rogue cow. A Heifer (Halfer cow) doesn't have great cowing bonuses, but Dwarf/Rogue might be able to get up there. They'd still be less useful than a Sage or Merch cow, and it's better to use Fae/Rogues to target cows anyway, but the option is there I guess? Never really learned much about cowing, except how not to do it...