I haven't caught that many on my AS yet (I seriously lack the motivation atm) but the ones I have caught were disappointingly easy. I mean, Rayquaza you HAVE to catch, but when my ultra ball only rolled once before clicking shut, I was amazed. I remember a six hour coach ride, several resets and over 300 Ultraballs (in total thrown) to catch Regirock, but now, it's not even taking 50. And the animation for the legendaries coming from Portals is also a bit... lacking. I mean, Lugia dropping from a hole into a disappointingly lack-lustre stage is anything but inspiring. But hey, they wanted every Pokémon to be catchable between X/Y and OR/AS. So they had to find some way of getting all these legendaries on one stage.