Character Card Deck effects

Something I overlooked with my assertion that you only need one S Rank, or one A Rank, or whatever to get the S Rank or A Rank, respectively, effect is that I always had two of the highest level, for example, two S and one A card, or two A and one B, and I got the maximum effect. However, I looked at one of my set effects in kMS today, one S, two A, adventurers, and the set effect was listed as A Rank. So, I believe that the set effect is based on the majority rank, so to get S, you need at least two S Ranked cards, etc. I don't know how three different ranked cards would work, however.

From what you're saying this is what I understand:
Since I've got a Buccaneer and Cannoneer at S rank(120-199 range) and a TB, I would get the S rank 3 Pirate set? Or does it only work for the Hero/CK/Adventurer/Resistance sets?