I'm generally comfortable with loose tiers rather than trying to create much definition between them because there can still be significant difference between two characters of the same tier that just happen to sit on opposite ends of even just a subsection of the tier.

As for numbers, they have their place. Often they can be overused. Rarely should someone need to bring up specific numbers and calculations in a battle. Primarily, I used it to keep track of specific distances so I can keep a sense of how much time is taken up when addressing movement son the battlefield. There are a few other uses for it, such as when strict comparisons need to be made, but those instances are rare in my books.