I agree with the OP in a sense. I miss killing Elites in Campaign. Still don't fully understand why they were removed (Sad Face)
I've had a lot of bogus happen with Elites, More prominent with Elites than Spartans, But then again I've also pulled off some heroic shots on them.
Really, it depends more on lag then the character model. I find that most the time in SWAT your coming from the side of someone anyways, and that's where the Elite is weakest. Rarely do you come from behind cuz people are wary of the no motion tracker, and when you do if they choose to fight they have to turn around anyways and when they do, that exposes the side.
Killing Elites just takes a slight more adjustment.
Oh, and of course to kill them from the front is even easier than Spartans. Most people aim at Chest level anyways, So why even change where your aiming? Their head drops to their chest.
Yes, There's some bogus with them every once in a while. But then again there's a lot of Bogus with Spartans too. I've experienced teh same problems with both character models.