The achievement is somewhat broken. It was 20 seconds, now it's 14 which makes it close to impossible unless dalaran is empty and you're a lucky spambot. So people resort to click software, which is illegal obviously.

Even got it's own topic on achievements forums on wow-europe.com. An enjoyable convo from there:

Karuna: "For anyone worried about the program ( as i was initially) , just check my achievements and you'll see that i've just got the juggling one about half an hour before this post. I'm not a hacker, this program seems genuinely ok and the site it's downloaded from looks legit too.

Shadarknight: "It's also technically a bot program, so you ARE cheating, so enjoy not only your ban, but hopefully lose of the achievement.

(auto-clicking = you are not doing it yourself=botting) "

Karuna: "Even doing it like that probably took me 3-4 goes. If it's still hard with the program, there's something seriously messed up.
And pff, botting? Don't make me laugh, you're talking out of your arse. Technically? "

Shadarknight: "Ok, LITERALLY cheating, better? You're not doing the mouse clicks yourself, thus it's botting. "

Karuna: "Mate, not only does you opinion not matter in the slightest, you 99% don't know what you're talking about,, but I also consider your wishing for me to lose the achievement and get my account banned to be pretty damn despicable. Go away and darken someone else's life."

Shadarknight: "So... wanting a cheater to be banned is despicable now?"
Felt like sharing