I camped this guy for a few hours with some guildies of mine. There seem to be always 2 Meeda Hune in zone (always around the center area). Meeda Hune Soldier and Hero seemed to be the common spawns while Dancer, Noble, Hatter etc. are rare spawns.
So to get the Hatter just keep killing the two Meeda Hune mobs in zone toll the Hatter spawns.
DON'T even TRY this without a TRACKER though !
I hope this was helpful.
Matronmalice, lvl 45 Cleric <Legions of Lolth>