We too seem to have a large percentage of coy-dogs. Bigger, less fearful of humans, etc. Consider that a pack of feral dogs is generally more destructive, mean, and just plain viscious than most any group of "naturally" wild critters. Now cross them with a critter with an uncanny sense of survival & stalking, a super learning curve, an already developed sense of "pack attack" and you have....well, let's see....you have, ummm.....well, a really efficient predator that will also eat carrion or anything available.
In the very early 90s when I started seeing coyotes fairly routinely while hunting, I would guess most were in the 35# range that I saw. Last few years I hunt less, but those I see are bigger. I've seen a couple of dead ones that were in the 50# plus range, maybe a bit more. Those clearly had a different head shape, and a thicker body, but were definitely not domestic dogs...likely first or second generation crosses.
We had two Lab/Border Collie crosses...SUPER dogs, app. 40# each, hunted in tandem. I've seen them pull a racoon off each other, I've seen one lay up in a low spot while the other worked a field to drive game to her sister (they got a rabbit as I watched), etc. Tough, savvy dogs. They encountered a coyote (maybe more, but I doubt it as they made it home) one day and suffered numerous bites around the head and neck. From that day on, they cowered when they heard one howl.