In the case of Julian vs Bill, you might also have to take into account these two guys have been playing eachother off and on for like 10 years. This doesn't necessarily fall into the idea of "See, it's a matter of the person who uses the character.." situation because it's so specific. To get an idea of the actual character's effectiveness it is more important to look at the "people who use the characters well" meaning, the player pool, because obviously, if no one uses a certain character still even 12 years after a game has been released, that character probably sucks in general.
There are in some cases, people who use the lesser effective characters to their highest potential, but they still struggle against the high tier characters. These two know how the other plays even beyond standard character tactics, and this is where the whole effectiveness thing comes into play. I've seen Bill defeat Julian's Sektor with ease, but I've also seen Julian beat Bill's Kabal consistently. I'd say Bill's constant attacking is his only weakness, but I really only know a few people who can beat him.
