been running into this problem myself, namely those damn chicken escorts, however, I found out that if you first make sure every char talks and gets credit for the " find XO11 bla bla...", and start it with a slave, accept with my main, and it cleary states in the chatlog that all chars have the quest, then I just sit tight and wait for the failed notification...

After that, i remove the failed quest from the log on all chars ( I know you dont technically need to anymore), and then I start it with a slave, and that has worked for me now 4 out of 4 times...

Sucks to be forced to do some extra stuff to get it to work, but the tanaris escorts (quests) you just donīt want to do too many times