Yeah, when your character is stronger, you do get away with things easier, and that's why people tend to blame tiers so much. But a good player will be a good player regardless of whether the character is strong or not. They may win or lose based on the character strength at that point.
I'm not arguing against you, I agree with what you're saying, I'm just saying it doesn't change what constitutes a good player. The player may get even better defense by playing that character with weak defense as a result, or lazier by playing that strong character, but usually, a good player will still keep the qualities that made him considered a good player to begin with.