The monsters and builds in the Top-Tier Builds, DLC Builds, and Notable Monster Builds were debated and refined by most of the advanced and expert players who frequented these message boards. Those discussion spanned 9 full threads (500 posts each) and petered out early into the 10th. The first post of that 10th thread contains links to the other 9 if you'd like to read through all of the backgrounds: http://www.gamefaqs.com/boards/619315-final-fantasy-xiii-2/64497740
So, while the first response was undeniably sarcastic, that FAQ really does contain the results of the experiences of numerous players. I was not in any way being sarcastic when I linked to it.