Our blaster is the Wizard. He's slowly coming into his own with Cones of Cold and Chain Lightning.
But that's at level 9 or 11. If you ask me, that is criminally late.
Seeing him cast Fireball on all four monsters of an encounter (there are very few encounters with lots of mooks) to deal maybe average weapon damage three of them, the fourth taking no damage at all, was pitiful.
He just expended one of his few highest-level slots, and it basically made no difference. No creature was dropped. Sure, it means one hit less is eventually needed for the martials, but that is a very low and unimpressive impact. The amount of incoming damage saved felt inconsequential.
Certainly up until level 7 I felt there are zero reasons to bring along a Wizard. A second (fourth, actually) martial would have been much more helpful. Another martial would definitely have made an impact where it counts: not only by reducing incoming damage faster by actually dropping enemies, but possibly even more importantly, by being far better equipped to soak incoming monster attacks.
The session before last, when the Wizard managed to insta-kill several mooks (from full hp to zero in one go) with his Chain Lightning, was the first time I recognized the power of magic. Everybody around the table cheered, relieved the player and character finally justified his place in the group as somebody capable of doing something the martials simply can't.