There's also enemy defense to consider which, when approaching high levels, favors base stats (* keyblade multiplier) over the multipliers of skills/abilities/crit/element.
If I'm not wrong, the formula is something along these lines:
((medal ATK * keyblade multiplier) - enemy defense) * (ability * guilt * skill activation * elemental weakness * crit) * 0.3
That first block is the most important. The higher enemy defense goes, the smaller that number, and it doesn't matter how much the second block multiplies a small number.
Therefore, with the way the game is balanced, going from 7k to 8k base attack from Chip & Dale medals is a far, FAR greater damage boost than it seems at first glance. If an enemy, say some high level Morning Star, has 12k defense, and your medal is in a 1.8 multiplier keyblade slot,
(7000 * 1.8) - 12000 = 600 x skills/abilities/etc
vs
(8000 * 1.8) - 12000 = 2400 x skills/abilities/etc
It's also why the seemingly incremental upgrades to the multipliers actually do a shit ton (and why Olympia at x2++ packs a wallop)
Of course, conversely there are HP sponge bosses with low defense, like the card stack which is more what-you-see-is-what-you-get.
edit:
I think most tier lists assume max guilt. Otherwise the musketeers wouldn't be so high.
Yeah, it depends a lot on what people want Tier list to represent.
No no no no, what I meant is Limit Form generally seems ranked higher than Black Coat Riku which is an identical medal of a different color.