So did madara ever fight seriously in the last arc?

Yes, it is in his personality to belittle his opponents that he doesn't consider worthy to fight and just play along with them like the five kages. Madara was very overpowered at his point, and when he became the host of the ten tails there was almost no chance of stopping him. Henceforth, the only shinobi that were a match for him were those who used Six Paths or all gates. Even so, he played with Might Guy and even laughed at him. The only ones who actually posed a threat to him was Naruto and Sasuke. If I were to put Madara on list, he would be on par with pre-jin Hagoromo.

Now it is very debatable whether he could beat adult sasuke or naruto, because each of them could fight against him evenly and even overpower him on some occasions.

/r/Naruto Thread