Shield bonus is affected by Ability Strength, but the amount per second also seems to be an average instead of a static number, and can fluctuate for each tick dealt on enemies even if the damage remains the same.
Mods like Fast Deflection and Fortitude can be used to increase Volt's shield recharge rate, allowing overshields to add up sooner.
Enemies inside of Vauban's Vortex will all be hit at the same time, and will shock every enemy inside at once causing potentially massive bulks of shields each second as well as increased DPS of the ability. This also allows a low Power Range build to be viable.
Casting Electric Shield before casting can prevent some damage to Volt and his allies when casting, as the base ability prevents Volt from moving, and may only slowly regenerate shielding.