Don't forget about Refinement specializations and foci bonuses.
When you are talking about Epic/Legendary skills, it isn't insane to assume +2 or +3 specializations and focus bonuses. So that can be another +4-5 for EACH.
Thaumaturgy [3] gives 1 point of specialization and 2 item slots.
Evocation [-3] gives 1 point of specialization and 2 item slots.
Refinement [-1] can give 2 points of specialization.
3 points of specialization can get you +2 Accuracy (offensive and defensive) in X and +1 in Power (offensive and defensive) in X. (Remember highest specialization bonus is capped by Lore and it follows the same balancing rules that skills do).
2 Item slots can get you +1 offensive accuracy with 1 element and +1 offensive power with 1 element. (I am assuming the other items are used for defense or whatever since this is a low Refresh character)
Wizards require The Sight [-1] so these together is -8 refresh.
Assuming a Submerged game, Superb Conviction and Discipline give you +7 (5+1+1) and +8 (5+2+1) when attacking. So even with a Power 7 spell, your target is resisting 8+4dF, even if a target has an Athletic stunt (like Acrobatic), they maybe get +1 to dodge. So unless your target has Athletics high on his skills, they are going to get hit (well I guess full defense can help, but that means they aren't attacking you).
As an aside, once you get to a point, Discipline is better than Conviction. As excess Discipline gives extra shifts of damage which a target that exceeds Discipline takes no damage at all.
But I think this whole 4-6 shots a scene further supports the "it's easier to just use a gun" argument.
To me, evocation magic represents a "pocket bazooka" not a sidearm. You don't see a lot of military units carrying that many shots.
The limit on shots is a good reason for wizards to not get into the same zone as their target. Dresden of Storm Front has Conviction 5 and Power (Fire +1) for a "Fire Conviction" of 6. If he were being rushed by 4 vampires who are all in the same zone (but he isn't in there), he is better off going with 6 shifts of power split for Weapon: 4 and 2 for Area. Even still he probably wants to spend a fate point to power up his Discipline roll (probably "Not so subtle, still quick to anger", to get it to Fantastic (+6) before rolling 4dF) since Rampires have Athletics Fair (+2).
At Fantastic, Dresden doesn't have much to fear (81.5% chance of having at most 1 level of backlash, which is worth taking in this case). With Athletics of just 2, there is a good chance the Rampires are going to face Weapon: 4 + at least 2 (so 6 physical stress). They are going to have to tap into their Feeding Dependent powers. However since it is a zone filling attack, there is a question of whether the Armor: 1 of their inhuman toughness applies (the fire is EVERYWHERE). So they are going to start taking consequences (can NPCs take consequences?) or get taken out fast. (There is like a 81.5% chance that they only get Athletics 3 or worse on their roll, which would be 7 physical stress.)
The attack margin jokes about using shifts of power for movement, but it didn't seem to factor in applying movement to your target. I think it would be fair to apply 2 shifts of power in exchange for moving the target a zone. In Fool Moon Dresden blasts MacFinn through several walls, then across a street. That sounds like a LOT of zones. In the case of vampire attacks during the day, I imagine launching them out of the shadows and into the open sun is probably a more effective strategy.