How many cloak of Flames are on the server
 

That don't "belong" to a guild.

How many pickup groups have killed Naggy/Gore/other dragons who drop it?

There should be a few that don't "belong to a guild." There were guilds that got a cloak then fell apart and there were players that got cloaks and left their respective guild. I can recall of at least 2 being sold and that was a while ago.