What I find most powerful about that spell is the "Aggro from this does NOT go to the caster" part.
So you basicly lose your elemental to gain a strong finisher spell and a shopkeeper (just for an example) on your side.
How do you get a shopkeeper on your side? Aggro does not go to the caster, aggro does not go anywhere. No one gets aggro from the spell. So the shopkeeper wouldn't aggro on anyone. Certainly not on your opponent. That would be redunklulous.
Maybe give them a bit of melee potential as well. Perhaps something as simple as empowering themselves defensively to get balance, and offensively to get elemental fist damage types. Like adding in flame fist, ice fist, shocking fist, etc etc.
While a neat idea, there would be no reason outside of PvE when the elementalist is not tanking when they would ever not be in defensive. And I was thinking they would be getting abilities like that while under the influence of One with the World. 
While a neat idea, there would be no reason outside of PvE when the elementalist is not tanking when they would ever not be in defensive. And I was thinking they would be getting abilities like that while under the influence of One with the World.
I can think of many times I would not be going offensive 
. To fight anything that does not bash (trip is negated by flight) I would be going offensive to pour in that eensy bit of extra damage.
And flight is negated by dispel, air thrash, hurricane, haymaker, and several other things... The only classes I can think of off the top of my head that you would want to go offensive against would be Invokers, Shamans, Clerics, Healers. Assuming they didn't have a pet that bashed/tripped.
This class seems rather interesting...
Perhaps, if you changed the name of the Hellball spell to Nature's Wrath or some such and had the specific elemental summoned do specific type of damage instead of all elements, for instance the Air Elemental could actually become a Tornado that could work as a way to randomly throw your opponant around the area, giving you time to flee...or create a hurricane version of firestorm as well as a chance to lag...the Fire Elemental could burst into a firestorm sending out fireballs to accumulate decent amount of damage...and so on and so forth for all the different element types
I think it would require a specific Elemental to go after certain racial vulns or to offer certain abilities that would work better against certain classes...there is so much that can be done with this idea.
I would prefer the abilities to all be different depending on what Elemental you use when you "sacrifice" them...not only offering diversity but a way to balance it too...IMHO
Of course...elementals that were not augmented by Elemental fury and such would not do as much damage as one at it's full potential...