Mages are adept at taking down multiple mobs at once, but require specific conditions to be ideally successful. There are several areas that may look temping, but are often hard to use. Here is a list of those spots not to use, and why.
The Ogres of this area have a kick that locks out spells. Boss Grog'ak has a knock-back effect.
Clefthoofs (All Sorts)
The Clefthoofs look tempting at first, but their stunning stomp (much like a Tauren's) will stun you for 3 seconds. These also tend to come all at once, so a pack of Clefthoofs all stomping within 2-3 seconds of each other... You get the picture.