This isn't typical Coyote behavior. But they are very smart animals and are quite capable of learning new behaviors.
There's a (locally) famous pack down near Death Valley that stakes out rest stops and kills pet dogs. A tourist will stop at the rest stop and let their dog out to go potty. One of the coyotes will hide nearby, and run off causing the dog to chase. The rest of the pack will be waiting to ambush the dog when it's far enough from its owner.
When you have a large aggressive pack, gaurdian animals probably won't work. They'd make a nice meal of a llama and with an advantage in numbers are capable of killing large dogs. Usually coyotes won't take the risk, but if they have lost their fear of humans all bets are off.
You need to kill as many of that pack as possible and strike terror into the hearts of the survivors. The best way is with a rifle as the association with human activity is strongest. You want to train them that humans equals death. Traps and poison are also good, but the association with humans is less strong. Better fencing just makes their job harder, but doesn't teach them a lesson.
Once you break this pack of their habit, you need to maintain the lesson by continuing to persecute them. At that point guardian animals should be effective again.