Electric aura weak?

Is electric aura weak? compared to my harpoon it seems that the electric aura will do less dps. should i still use it ?

If you are looking at a single target, yes the aura is weak. The point of an electric aura is that it can apply damage to (essentially) an unlimited number of targets at once. You can use it to clear out trash mobs (goblins, kobolds, archers) so that stronger towers can focus on bigger prey.

And it works better if you combine it with tower to slow down mobs: ensare aura or gas trap.