Pandemonium Warden is already in the game, anyone playing already has the option of fighting it. The article you read was one filled with inaccuracies.
Firstly, he is NOT a boss. He is an extremely difficult OPTIONAL monster which people are hoping will drop some very nice gear or weapons. Second, they did NOT beat him. They spent 18 hours trying to figure out how to beat him and were unsuccessful. Third, it does NOT take 18 hours to beat him. The more difficult monsters in FFXI are designed requiring players to utilize certain strategies. Without them, some of these are near-impossible to defeat. Pandemonium Warden is one of two monsters we have yet to figure out how to defeat.
Also, in FFXI, you dont pay to download new content. The subscription fee covers the cost of their servers, the developers time, resources, and work, and the downloads.