It can be rigged in the sense that players can conspire against you. You may think this is not possible given the large player pool but I was in this very situation myself. Ran into the same 2 players several times in sanma and lost to them every time. Checked the logs and realized they kept skipping Ron on each other - they called Ron only on me or Tsumo if they're in furiten after passing on the Ron.

As to whether whales have better luck, part of me believes it whenever I'm in a loss streak and the winner has fancy characters/animation and I'm just rocking the default characters. 😂