Leona is NOT bottom tier, surprised we're not past this assumption yet. Neither is Billy, especially after his b+A xx spinny staff free cancel tech, he gets great damage.
Why people continue to say both those characters are weak is beyond me. Billy has a smothering pressure game when used properly. Not just that he converts counter hit C+Ds into large combos way easier than 95% of the cast with his f+B pogo hop. He can confirm a counter hit into a 40% combo from a decent distance away and in some cases even mid screen!
The thing with Billy is he is a character who is a no thrills character in the sense that his game plan seems bland, but it is very effective. It's all about controlling the opponent once you hit that sweet range.
I can't say much about Leona, but with Billy it's probably the feeling about his reward for playing his poke-based defense isn't as good as what characters with strong offense and damage get for when they do crack him open. I personally think David's list has him below where he should be, though.
Defense? Billy is an offensive character. His game is not about opening you up fast it is about grinding you down. He basically is a character who controls you. The thing about Billy is he doesn't even have to be doing anything for you to be in a bad situation.
The thing is though you need to have a really good set of fundamentals and be able to anticipate your opponents moves to make Billy scary, but if you can do that Billy is one of the best point characters IMO. He doesn't need meter to work his core game.
I guess we just define stuff differently, because even though Billy's rush-down works at midrange I look at his game plan of walling off your options with his pokes as being more defensive than your typical Kyo-style rush-down, but I won't split hairs over semantics here. The point was that I think people underrate Billy because they view his ability to actually get combos off his hits to be relatively low and even though he has you trapped if he ever screws up or you find an opening against him you can respond by dealing all that damage right back to him in one go, depending on your character and the opening you find.
Again, I do disagree with that view of Billy (I think he's pretty good), but I'm giving my possibility on why people might underrate him. They do so at their own risk, IMO.
Also I hope we've got some surprises waiting for this year's Evo. Last year's stories were Kim (the strongest overall performing char at the tourney), Duolon and Chin. For some reason I'm thinking Ryo, K', or Daimon (if not all three), especially Ryo. That dude scares me.