I don't know a ton about him, but from the little I've seen and heard about Abiamiri, he seems a great fit in Atlanta. Another name to keep an eye out for is Michigan's LaMarr Woodley. Although many have been talking about him playing OLB in the NFL, he has the sort of speed and range that I know Mora & Co. prefer.
I'm not sure about this DE class, but it does seem like there already are 5 or 6 seniors that could be taken in the Top 40-50 picks. ANd if some notable juniors declare, that improves its depth.
As far as the corners go, it's not as deep as it was a year ago, when you had all those DBs going early. This is what I've heard about the few that you have listed:
Hughes - great size and athletic potential, but purely a raw zone cornerback. Unless the Falcons plan to go to zone all the time, they should probably stay away.
Bennett - I hear he is better than Jonathan Joseph, who was picked in Round 1 last year, but for some reason my brain is connected character issues with him, so does he pass the filter?
McCauley - Most say he will be a Top 15 pick, so is he out of the Falcons reach?
Cason - A top cover man and a junior, but I hear there are concerns with his speed. Plays at a top level, but I hear his stock will be connected to his speed. If he times well, then he'll be a Top 15 pick, if not he might drop to Round 2. So he's a wait and see guy. Sounds like a guy that would fit here, but may be out of reach.
Revis - Another junior. Being a Pitt alum, I like Revis, but to be honest I have yet to see that much out of him that says he's anything special, at least to merit some of the draft sites that consider him the best corner in the country.
We shall see how things play out over the next 5 or so months, but from a lot of things I've heard the gap between the CBs that are considered borderline 1st rounders now, and those that are considered potential 3rd rounders is not as big as when compared to DEs.