I would like to develop a 4th level Wizard/Sorcerer spell that functions like Produce Flame (but electricity instead of fire). Being a much higher level spell, I was thinking of having the damage be 2d6 + 1/level (max +10) per attack. I'm not sure if that is too good though. Other 4th level spells that deal damage mostly require saves for 1/2 damage and affect a large area (Ice Storm, Shout, Dragon's Breath) being able to affect multiple targets. But being a "to hit" spell, the target wouldn't get a save (if it hits) dealing 2d6+7 to 2d6+10 damage (with the possibility of doing double damage on a critical), once per round for 7+ rounds. Granted, it isn't that impressive compared to a Two-Handed Sword wielding Fighter that can attack 2+ times per round for the same or more damage per attack, but it allows a Wizard/Sorcerer to cast 1 spell and be "effective" in combat for 7+ rounds. This is one of the reasons behind the spell, to manage resources a little better with my Sorcerer.
If it is "too good / not good enough" what might I do to tweak it? I want to have something to propose to my GM that I can backup with examples if need be.