Well, it's understandable the Nutaku must provide special features/advantages to players willing to invest some money on the game, it helps the business, after all.
Yesterday I took some time to read the rank rewards, and so far the prize cards are actually available in normal gachas and chance rolls (many of us already got Akie Ibara and Runa Kamiwano during the event), so from that perspective, Nutaku is being quite fair with everyone.

I think that the main problem today is the massive HP guards issue, because it's getting some of us almost totally stuck, waiting for our friends to spawn a weaker guard. I'm OK with paying players to progress way faster than free players, the only thing I think it's annoying is keeping us stuck like this with those guards.

But in general the game is giving balanced chances. Personally I'm sad for not being able to get Satona Okada, but comparing the whole event, it's really fine.