1. It's a free attack that always hits. It can also Crit. I'm 90% sure +Crit Armor/Clothing & Accessories count for Drone Crit rate. A quick test had a 43% Crit rate with Witches' Robe and Trailblazer Hat (listed 25% Crit, 16 Crits in 37 attacks).
2. Electric is a pretty good damage type. Most Shields are weak to it, as are most robots.
3. It scales with Level. By Level 13, it does 14.0 - 21.0 by default. 29.0 - 36.0 with Drone Control.
4. You can get a 2nd Drone with the Combat Tail implant (though that's late in the game).
5. I generally find I don't run out of Shields, though that may be because my Drone Tech is also Melee.