So, my complaining worked.
I spent a bunch of time putting off my slot machine duties in Final Fantasy XIII-2 last weekend, and then when I finally went back I hit it big in roughly ten minutes. It took a while to get my first triple-9 (250 coins) and Victory Mode, but I almost immediately hit another triple-9 (500 coins) for Super Victory Mode. Only a couple spins later did the microchus line up (see above) for a massive payout of 50,000 coins; far more than the required 7,777.
Turns out slot machines aren’t that bad after all!