Ours are tall (GSD height) but yes build more like sight hounds. They happily kill and eat goats, sheep and calves. If you ever get to see a dead one and move it, there is no weight there. Here the gov has a bounty on coyotes. One of our neighbours lost 100 lambs in one season to coyotes.
They are so plentiful you see them in broad daylight. All farms around here that have sheep or goats also have donkeys, lamas, or Maremas. But you hear all the time of the farm dog running them off. Coyotes here don't tend to go in large packs as its counter productive. There is so much small game (rabbits, sheep etc) that a large pack isn't useful. (they will pack up if the game is large like older calves, deer). But generally coyotes live on mice, rabbits etc. I can't say I have heard of these ones killing larger dogs. (really a lot of LGD aren't that much bigger than a rottie, I know of MANY BMD that are about the same size just a little stockier, perhaps even shorter. If a rottie wouldn't be safe then I wouldn't leave out ANY dog) You do hear of the wolves killing dogs, or the hybrids.
There is a HUGE project in the conservation world with studying wolf and coyote DNA. Because some of the hybrids are viable and are pushing out the parental populations. I still say most fit healthy largish dogs have little to worry about a pure coyote. Coydogs and Coywolves are different though.
When picking a farm dog its useful to know what is around and what you need it for. I would never pick a BMD as they are short lived and aren't terribly athletic, when I think farm dog I think a dog who can hang out with the people all day, not a dog who just lies in the shade whilst you do the chores lol.
That said Bounce is an awesome farm dog. She doesn't bother with live stock, sticks around, is pleasant company and has a good coat for dealing with temperature extremes. Now she is too small to take on a coyote (she's 17 pounds) and likely wouldn't even try but I don't need dogs for that.