In all honesty, my problem with Ruo isn't that he's stronger, it's that he's a terrible rival, a good rival doesn't have to be an invincible existence until the end, many here, if not most, believe that the MC can only beat Ruo in the last book.
Now with the latest revelation, that the heavens favor Ruo, that may well be the case. What the author has done is practically turn Ruo into a Medaka and the MC into a Kumagawa (anyone who knows Medaka Box knows what I'm talking about). This guarantees that no matter if the MC gets a boost, Ruo will have a bigger boost, no matter if at some point the MC seems stronger than him, Ruo will show something new and stay ahead. It's exaggerated to the point that, if by some miracle the MC is winning, something absurd could happen to "save" Ruo.
Let's go back to the example of Aura Clash. Jack is apparently invincible at the moment and the protagonist's biggest obstacle, but I doubt that anyone who follows the game will think "It's only possible to beat Jack in the last book". Jack is a good rival, to the point that even if he ends up victorious in this book, no one will think "He's Anon's pet".