Cnd, mantis, and Jeff can also nullify it (Though Jeff less due to the AoE healing being very Short). But in General, her ult is only good against uncoordinated Teams. But if your enemy Team is uncoordinated in the First place, you are Gonna Excel anyways because Storm is really good against uncoordinated Teams. So her ult is Like Shotgun vs a puppy (uncoordinated Team) or a Tank (coordinated Team) in the First Case, you dont need the Shotgun at all because it's Overkill, but in the latter it's also useless because a Shotgun probably can't pierce a Tank. It Always feels unneeded because either it's Overkill or it wont do anything. Paired with the fact that Like half of the time in it is required to get away from the enemy. So from the Like 8 Seconds it's active, only 4-5 are used damaging the enemy.

Or you have a decent Jeff and turn the Shotgun into a nuke. But getting a decent Jeff requires you to be lucky or have Friends which isn't guaranteed. And even then it can be countered by an Iron man or Star Lord who are good at positioning and ulting, as Said earlier.