A poorly-placed Thunderstorm can send trash mobs flying across the room, much to the chagrin of your tanks and melee DPS. Hell, I've done it just to be annoying before. It works. But you needn't glyph it to remove the knockback. It's actually a far more useful ability without any changes.
Remember: You have the ability to aim the direction that your Thunderstormed victim will fly depending on the direction you're facing and the mob's position. Just because you can send a mob in a random direction doesn't mean you need to. Making them airborne with a purpose? That's the elemental way. Let's examine some of these purposes.
- Playing catch with your tank.
It happens, folks: tanks miss a taunt, you DPS a little too early, a stray add gets pulled. As most DPS, you have some kind of "aaahhhh!" ability to use to help. Rogues have Vanish and mages have Ice Block to drop aggro. Paladins have Hammer of Justice for a handy stun. You have none of those things. What you do have is the ability to turn a mob into a tank-seeking missile. Line yourself up between the mob and the tank and Storm away.
Now two things can happen there. The first is worst-case scenario: the mob careens toward the tank and doesn't get picked up, leaving an angry red 100% flashing at you above the mob's life bar. Even with this situation, though, you still have options. A quick Frost Shock or Earthbind Totem will allow you to to make a beeline for the tank and bring your angry friend with you.
The better case actually happens more often. Most of the game's tank have some kind of AoE used for generating and keeping threat, and a properly-timed Thunderstorm will knock the stray mob right into, making your threat meter a much more enjoyable color, like gray.
- One-way ticket to Snaretown.
On certain fights with untanked adds, like Deathbringer Saurfang, you have to rely on other ranged to do their jobs when it comes to snaring and focus-firing. Sometimes this just doesn't happen, and you need to take matters into your own hands. If a Blood Beast starts making its merry way toward you, knock it toward a Frost Trap or an Earthbind Totem. If none are available, the time the mob spends in transit back to you from its free flight ensures that it'll have reached its very final destination ere it reaches you again.
- Flying for a spell.
We have Wind Shear for interrupting spells, but in the event that it's on cooldown, Thunderstorm is a perfectly viable interrupt as well -- mobs, like players, can't cast while they're moving. You just have to make sure that you're not sending the mob too far away from the tank(s). Send them to a nearby wall or environmental doodad to accomplish your task without getting yelled at.
- Long way down.
Knockbacks might be annoying for fellow players in PvE, but in PvP, they're even more annoying -- just not to your teammates. Enemy players can be griefed to the Firelands and back with judicious use of Thunderstorm. Get a rogue off your back atop a tower in AV; prevent a cap in WSG by knocking them to the second floor; let them die to fall damage by sending them flying off the top of the keep in Isle of Conquest. All fine outcomes, and all genuinely satisfying.
Of course, the knockback isn't Thunderstorm's only component. Mana recovery is the main reason why raiding shaman use the spell. Being at ranged, you're far less likely to accidentally knock a mob away with it, and the no-cost mana it generates is fantastic on top of Mana Spring/Judgment of Wisdom, Water Shield, and Replenishment.
If you're a very hardcore, bleeding-edge type of elemental shaman, then you'll often read posts saying that Thunderstorm is a DPS loss, and they're not wrong in that the GCD you use for Thunderstorm could be used for other, more damaging spells. But the fact of the matter is, if you're having mana issues, using Thunderstorm is far less of a DPS loss than running out of mana completely. Thunderstorm restores, with about 25k in your mana pool, roughly 2000 mana. Over a 3-minute fight, that's 8000 mana, or about 30% of your adjusted mana pool, for the cost of four GCDs.
So, my recommendation is to use Thunderstorm liberally if you have any issues with regen in long-term encounters. A few global cooldowns won't knock you to the bottom of the DPS charts (though being an elemental shaman certainly might!).
Show your totemic mastery by reading Totem Talk, whether reading Mike Sacco's Elemental edition or Matt Rossi's coverage of Resto and Enhancement. New to being Elemental? Check our Elemental 101, your one-stop shop for Elemental basics.