This doesn't warrant the cost, compare to RoF
RoF can hit up to 23 creatures for 3 damage at 7|5
Grenade can hit up to 7 creatures for 3|4 damage at 5|7
The unupped is outclassed completely by Firestorm and even unupped RoF in most circumstances. Once the creatures get onto the bottom and top rows, RoF should already do more damage total compared to Grenade.
Missile is meh. The 7: fire cost is a bit much, should be 6
maybe.
And also, does Fire not have enough CC already?