As Sam said, saturation is probably near-impossible.

But even though I'm only dual-boxing two accounts, I notice lag between the screens. My follower shows she's right behind the main, but shows them about 15 yards behind where my main's display shows them at. When they're standing still, the instant I hit a keybind to make the slave cast something I hear the sound effect on my main's WOW, so it's kinda confusing, they seem perfectly in sync that way but when running around on /follow the slave seems to be a bit behind. Which makes navigating tight corners and spaces a little frustrating.