First of all~ easiest and most important for ME would be to make Dk-specific flirt/joke just like Demon Hunters have. Its obviously unfair that first Hero Class is not THAT special.
Second is that I would love to pick what I am going to say~ some vendor similar to transmog. There is few of them that dont fit class fantasy or your appearance… or are too stupid for user. There was already a thread complaining about female human jokes… you can add female night elf talking about her skin color or male night elf speaking like he is druid hero class. Also Blood Elf jokes about addiction are outdated lorewise!
I would like to pick one that is best in my opinion and keep spamming it 
