If you forget the bullshit of other characters... Hilde's Doom Combo, Kilik's Asura Dance, Algol's Bubbles... Voldo is who I would put as #1 in the tier lists. He has punish game, speed, damage, range, priority, is extremely safe, and an amazing BT A+B that auto-GIs everything. At my tournaments, there is an average SEVEN people who use Voldo, and that number is rising... The whole system of the game seems to be skewed in his favor. While the other 3 characters are top-tier becaus they have a single "bullshit" situation, Voldo just has it in the general design of his moveset...
There is something about SC4 that I don't like... the whole idea of characters being at disadvantage on hit so often. However, with Voldo, it is rare. He is usually at advantage so often; and if he isn't, he has some sort of movement that nullifies the disadvantage. I watch a lot of people play Voldo and there is a single aspect they all share; almost all of them keep on attacking at all times. They eat damage, they attack, you block them, they attack. They are always attacking; because its just something that Voldo can do. Very rare do I see "smart" Voldo players.
I think Voldo can easily be fixed by adding 2-3 frames to the recovery of ALL of his moves. Then he will be fine; they you will actually see people playing Voldo in a smarter manner. You'll start seeing Voldos worrying about safety and whatnot; because right now, they don't.