Good to know. Looks like I'll be needing a massive amount of rupees if I expect to level up Ruto, Darunia, Midna, Impa, Sheik, Agitha, and Zant more quickly.
It typically comes down to figuring it the specific pattern for everyone/every mission type.
This is totally correct.
Of all those characters, how you do the stage matters just as much as your level. So I'd try them at a lower level and see how close you get to A ranking them. I'm talking about the respective Lv3 weapon stages.
For Darunia, the Lv3 fort taking badge helps a ton. Getting this badge changed it from doing it in 17 minutes to getting it down to like 12 minutes. And you'll need the time (saved from the L3 fort taking badge) to kill the captains/enemy heroes you need to kill.
For Agitha, just spam the rhino beetle combo and make sure you kill the captains in the middle of horde packs to get the collateral damage KOs.
For Ruto, totally ignore both gold Cuccos. Just kill the captains you need to and kill the final enemy hero and you're done. Just make sure to kill the large horde packs along the way so you have around 1100 KOs when you race to the last enemy hero. You can get the last 100KOs in that final fort. If you're fast enough the allied base will not be taken.
I did Midna at a lower level than I thought I would need to. If I remember correctly you can avoid the keeps here and just race down the captains. And get enough kills. But I'm not 100% sure here, my memory on this one not so good.
Zant's one was tough, only because I'm not so good at his combos. I had to level him up quite a bit to like 65. And then I got it done, no fancy tactics here, just practice makes perfect. And remember you can get the last 100 KOs in the final enemy hero's fort. I say this so we know when to stop farming KOs and race to the last enemy hero.
Sheik's Lv3 harp I remember was a simple case of levelling up more (to like 60) and I got the job done. Nothing fancy. I didn't use all that many of the combos.
Impas Lv3 stages were not all that hard for me. I'd try those at the level you are now and see how close you are to finishing it with the A Rank. Her's were some of the first Lv3 ones I did. The X specials with both weapons are great for killing large horde groups fast for mass KOs. I certainly abused this. The Lv2 spirit metre badge helped there to get special attacks faster At that time I only had the one spirit bar. If you got a 2nd one it could help out as well.
Of cause this assumes you have all the Lv2 armour badges. I assume you need them all for damage reduction on stages without any favoured element. I did them all without any Lv3 armour badge. The Lv2 ones are not too hard to grind out.