I'm relatively new to the MB scene so I apologize if this is already a well known method for crowd controlling multiple enemies.

I use a leaderless/focusless setup running three boomkins. Using Hotkeynet's toggle fuction I am able to effectively crowd control three targets with relative ease.

I have a macro on each toon that says "this is your focus target." Using my current master I highlight an enemy and push a button. When this button is pushed HKN sends a keystroke to one of the three versions of WoW saying "assist the leader and set as your focus target." I then highlight a different enemy with my leader and push the same button. HKN recognizes the button and sends a keystroke to the second of three versions of WoW saying "assist the leader and set as your focus target." I repeat the process a third time and now my three druids each have a different enemy set as their focus target. Now when I hit my cyclone macro with [target=focus] each druid casts cyclone at their focus target allowing up to three mobs to be crowd controlled. They then go back to assisting the current master and DPSing away on their kill target.

The whole process takes six clicks. One click to highlight an enemy, hit macro button, highlight another enemy, hit macro button, highlight another enemy, hit macro button. Then start the pull with a burst of DPS, hit the cyclone macro, continue DPS. This makes four enemy pulls a breeze. (may use roots instead of cyclone depending on the situation).

This method should also work in arena as you can quickly set different enemies to be the focus target of different druids (or shammies, mages, whatever) and then CC appropriately. Obviously in PvP the enemies are hiding and making this much more difficult, but if LOS is there then you can quickly make the battle into a 3v1 for a couple seconds.