Storm has the feats to take on Thor and better without Stormcaster. The only thing I can see Stormcaster doing for her would be to maybe increase her durability and super strength, however, writers should simply have her use her powers creatively in a defensive manner to protect herself from physical attacks. Its nice for her to have some weakness like being less durable than Thor to fight the baddies as it provides opportunites for a more creative use of her elemental powers. Now, that said, in terms of power output/damage, she can go toe-to-toe with just about anybody...and then there is this whole other aspect of her power that Coates has added onto her. She needs to be fighting people like Heralds of Galactus, Ego, the Living Planet, Adversary, Shuma-Gorath, and others as well as people like Dr. Doom, a Phoenix Force-possessed Candra, Bogan, Dracula (he can boost his powers by feeding off the blood of enormously powerful beings like "gods" and "goddesses" to fight Storm), etc.
So, even without Stormcaster, she is not outclassed by anybody. Besides, I don't need to see her use Stormcaster to pull feats far Far FAR below what she's already done without it.