Sorry everyone for the frustration I was /forcequitted 3 weeks ago due to having a baby. This business decision is quite bold. Especially after having supported us for so many years. Hell recruit a friend was basically inviting you to multibox when it was first introduced.
There are many other options out there, and more so that are multiboxing friendly.
I've been dabbing in a bit of Everquest 2 because of the free to play model I don't feel bad if I only get to log on once a week. Multiboxing in it is extremely user friendly. Slap your characters on follow and target your main and they assist with any further macro's.
Also been meaning to try out Star Wars as they are releasing more new content and is basically an updated WoW gameplay/engine from what I can tell. It does offer a PvP aspect too that has "something" there.

Multiboxing will thrive as a gameplay style I don't doubt that. They'll have this change on record if they do uphold it to show bad business decisions in the future. The fact their sub numbers will take a visible hit will speak volumes to the people who do actually make decisions.

My suggestion is to cancel your account, even if you do plan on continuing to play. Just re-sub for another month afterwards and cancel it again. You still get the time you paid for.
But in the notes type out exactly why you are quitting and copy/paste that onto each of your cancelled accounts. This will get the message across. Speak with your wallet, I guarantee you it has a larger effect than the forum.