In my honest opinion, ANY game (especially MMOs) should be made for 64bit computers. Any computer manufactured in the past... 5 years (possibly more), has a 64bit processor, and anyone running at 4GB (or more) of RAM, would be foolish to be running 32bit OS.
"32bit game for maximum compatibility", sure if you want to use that excuse. Let's take a look at the games system requirements (from it's Wikipedia entry);
Processor: AMD Athlon 64 X2 Dual Core 4000 or better / Intel Core 2 Duo Processor 2.0 Ghz or better
Guess what? BOTH of those alternatives are 64bit processors. There is literally NO excuse to have built the game for 32bit, when you put 64bit hardware as a REQUIREMENT to run the damn game. No amount of optimization on their end, will ever solve the underlying problem, if they continue to limit themselves to 32bit maximum.