All the character development pointless? Because of that, Londo has now the courage to say yes to the Drakh and sacrifice himself for the greater good of the Centauri Prime, even though he will know that he will be a prisoner for the rest of his life, isolated from his friends and happiness. And after roughly 18 years from that point he will save Sheridan and Delenn because he understands that is his only chance for a true redemption. The current Londo has that will power. I wouldn't say the man from the first season would do the same things.
Like many have already said, Londo is indeed a tragic character. He is essentially one of the good guys, who just made some really bad choices to gain power, but he still has to pay the price for his actions. He is likeable and you don't want to see him suffer nor make all those bad choices, but that just makes the resolution more emotional and powerful.