"Those that are mastiff like, are mastiff like because people have crossed them with mastiffs, and often to produce fighting dogs or personal guardians/pets rather than livestock guardians"
Id have to say you nailed it with this sentiment. The most sought after in Military work was the CO and Sar, and it is undeniable what is in there that makes them different. Think of it like this, an EB is a bastard of a dog but a cripple, give it a capable body and you now have a capable bastard. Same with most mastiffs, their bodies betray them. So cross them with dogs that are very wolfy in build to clean them up and add a bit of sharpness to their inherint aggression, and you then get monsters of old once again. Atleast that's how I think of it.