So, Darkmoon Faire ends tomorrow, and you only have 200 grisly trophies. And you are sick of grinding dungeons for them.
Easy solution? First, make sure you have your Darkmoon Adventurer's Guide so you can collect the trophies.
Then, head on up to Icecrown, where the Converted Heroes come in packs of seven and can easily be aoe'd down. There's also groups of cultists near the Argent Tournament grounds that can be rounded up and aoe'd as well.