Okay, so I don't sound armchair-y, I might as well give a line or three for each of my rankings. And no, I haven't tested any of these cards with proxies. I evaluate their card as it is in a vacuum stat-by-stat, ability-for-ability.
1: Kisada - A character that immediately gives your opponent a minus one on the first conflict is already good, even if its just a throwaway effect. If it happens to be a triggered ability from a card already in play, that's still one wasted ability that was played at a less-than-optimal time. And it gets better as the Crab player continues to win conflicts, as that effect is conditionally reusable up to three more times. The opponent will eventually run out of throwaway effects for that turn. The fact that his ability forces you to play around it all the time is already an indirect advantage. Of course, that ability is nothing if Kisada can't capitalize, which is where that 7 Military comes in. I can imagine that there will be times when Kisada wins the game just because the opponent didn't have an action to burn to allow a send-home or discard effect to resolve.
2: Shoju - He is in many ways similar to Kisada in that he has that impressive 7 Political that will draw in a card or two from the hand or force the opponent to over-commit characters to defend (or attack), as well as having an ability that's scary just because it's sitting there, waiting to minus you. There's not much to say about Shoju because he is simply good at face value, but his ability is easier to dodge compared to Kisada's, which puts him at a (very) close second.
3: Yokuni - He would have been my number one, but he is very highly dependent on the presence of other characters that have beneficial effects. If there are none, then he's basically a character with balanced stat lines, which is still something. That being said, the ability will make your opponents think twice about unleashing a powerful character of their own such as their Clan Champion, as Yokuni will likely be a better version of that character especially after Glory has been applied and he is practicing the Way of the Dragon.
4: Tsukune - Despite what I said at the beginning, I cannot rate Tsukune in a vacuum; I don't need to relate her to the in-Clan cards, but I can still evaluate her based on how often the game state changes and is affected by player decisions and the cards that can be used during conflicts. Her ability compels the opponent to think ten steps ahead and try to predict the ways the number of unclaimed rings can be minimized by the end of the Conflict Phase. Again, it is an ability that is scary just because it's there, waiting to explode into something.
5-6: Hoturi/Toturi - If it weren't for their 6 Military/Political, they'd be bad cards, in my opinion. Cheaper characters have more useful abilities compared to them, as the benefits come from very situational conditions that their respective Clans can achieve pretty easily. When it comes to ring-based benefits, they don't even come close to Tsukune who is supported by the abilities of almost her entire Clan.
7: Al - Bad stat line and bad ability in a vacuum. Even with the rest of her Clan considered, she will have to rely on having specific cards and events happen for her to fire off her ability even once; and even when it does, it doesn't seem very impactful.