What is the PSS? Haha, sorry, I have not played Pokemon since DPPtHGSS. ORAS has made me an active player again. ^^;Yeah its catch rate is pretty high, I think its because you HAVE to catch him to make the story keep going.
I kept killing Deoxys so I SR the game a few times and every time I was able to catch Rayquaza easily. Not sure about Deoxys being easy to catch though, that one took some effort for me.