I am finally, after well over a year, finished with all of the world event achievements. The Mask Task has gone from being a horrible, horrible grind to something that was fun to finish up. Don't forget about the 150 token pet that you can buy for your pet achievement! This Hallow's End should see you pick up two more pets for your 150 pets achievement.
A complete guide to doing every world of warcraft achievement, starting from nothing.