The Izuna drop has been really easy to pull off since DOA3 because they made the whole input buffering system way looser. It's one of the few cons that DOA3 has going against it but it's basically possible to just spin your thumb around the d-pad and the only thing that requires proper timing is the button presses but those are much more loose than other fighters. I was struggling with King's even simplest moves, having only DOA-experience, haha.
Yup, air throws were introduced in DOA3. They were also useful there to boot, unlike in DOA4 where they're almost impossible to get.
The Izuna also didn't do nearly as much damage in DOA3 unless it was HI-counter or off a cliff.