I'm just going by a gut feeling. Looking at his forward and back throw, seems like it has some endlag when he is switching from a dragon back to a human. Hopefully we don't have to wait for his changing animation to perform another action.
Based on everything I've seen, Corrin is looking pretty solid. If he were to have good throw follow ups off of down throw (looking at the down throw in the trailer, it looks like down throw should lead into something
http://smashboards.com/attachments/vzwjx-gif.88752/), then he'll definitely be high tier in my opinion. And maybe, just maybe, an up throw that kills? That would be the icing on the cake.
Dragon lunge looks cool and all, but a character is gonna need more than a gimmick to be viable. And is this meta, having a good grab game is key. He might be the first top tier swordsman character in my opinion minus MK. And also might be Rosa's worst nightmare if he can fsmash luma from afar without worrying about getting punished.
But all of this is my own theory, so take it with a gain of salt. But if the pattern continues with new characters (not veterans) being really good like Ryu (top tier) and Cloud (high tier) then Bayonetta and Corrin just might also be very good. I'd say at least high tier. I hope so! I love characters with wings and swords! Pit is my main if you haven't noticed ^-^