It seems like it was intended to compensate somewhat for a mage's slow casting time.
Unlike most offensives spells, the spell lasts an entire melee and allows the caster to make repeated blasts (one per attack) for that time.
From the RUE Eratta thread:
RainOfSteel wrote:Killer Cyborg wrote:Electric Arc works differently from most other attack spells, though.
I believe that the core of a full re-write of the spell for RUE would be:
"This spell, when cast, fires an electric arc at a target. If the caster retains any available attacks after this spell is cast, then additional electric arcs may be fired, one per available attack, until the end of the melee round."
This retains the flavor of the spell, without dramatically departing from the way other direct-fire attack spells operate.
If a spellcaster has six attacks, and they cast this spell as their first attack, that's six electric blasts.
That would be a good way of doing it, but it doesn't seem like that's how it should work.
The only part of the RUE description that is blatantly wrong is where the description says it takes 2 attacks to cast.
But discussing the spell made something occur to me:
How would this spell work in a TW gun?
Sure, it would work however the GM wanted it to... but the nature of the spell makes it seem like it could create a gun with an effectively huge payload.
Say you make a Fire Bolt gun that can hold 20 charges.
That's the equivilant of 20 castings at 1 blast each.
An Electric Arc gun, on the other hand, that held 20 charges would hold 20 castings, which would be something like 60-80 or more blasts!
Sure, the damage is kind of low, but that's still pretty nice...