Well, we all know it...
You made your way from bootybay to a capital city or used your stone for a trip to shattrath and want to cause some major havoc and then you get cleansed by one of these filthy bastards called Argentum Healers who are guarding the place...
HF running back...
Well there a big bunch of ways around this scenario.
Mages can use their invisibility as someone posted before.
Not a mage? Not a problem.
You can use a bandwith limiter like DU Super Controller or anything similar, download the free trial, there are enough cracks out for it but I don't think I'm allowed to post them here...
And if you don't want to download anything you can just pull the plug or restart/reconnect the router via control panel (I said restart because that usually lasts 10 secs, if you
disconnect -> run -> connect again thats too long for most peops around here and you get probably a disc)
So what we do is: we get our plague from the crates in Booty Bay and heartstone to the scryers/aldors inn or go in front of the healer-guarded way. Now run a little bit closer, but stay far enough so he can't cleanse you.
Then do your thing, restart router, limit via programm, pull the plug, everything works. Now while there is no traffic just run out of the door and around a corner to somewhere the healer can't see you (Be Fast!).
Now replug, turn limits off, whatever and after 2-5 secs WøW should run normally again.
/cheer! You are in!