Blanket statements: Not all Warhammer 40k codex are balanced. Not all Warhammer generals are balanced. Not all army composers are created equal. The question then becomes: What to do about it? The general principle in the community semes to be 'let the older codex rot, let the poorer generals suffer.'
Well I come from a sports background, where they deal with much greater numbers that 40k tournaments, and to keep the spirit of competition alive, and to make individual matchups more exciting, they have handicaps and grades.
Golf handicaps are the most obvious comparison - You play against yourself to obtain a numbered score. If you get the course suggested score (usually 72), your handicap is zero. If you play poorly, your handicap goes up. Just say you have a handicap of 10, you can play a game against someone with a handicap of zero. You compete to beat 82, they compete to beat 72, and you efforts can be compared.
Sui and I are playing a basic handicap campaign. Each loss means the looser gets a handicap of 5% army composition per loss. A win reset the handicap.
One of the main questions is: What does the winner get? More opponents and a broader experience of different armies. They get the considerable satisfaction of a win, and they get to fight a harder game against weaker opponents - which will hone their skill.