Takes the same amount of relative time as every other skill... one GCD. The animation is absurdly slow, but that is a visual issue more than anything.
Energy blast adds another high damage attack to a rotation, and generates ammo to allow for longer rotations overall.
It's a nice extra cooldown, as well. I usually follow all of my High Impact Bolts with an energy blast, due to the similar cooldowns, and it allows time for the stockstrike cooldown to proc.
Edit:
Put the points from Ion Shield to Static shield. 2% is a laughably small damage mitigation, and is better served by Static Shield's 4% damage reduction after using Ion Pulse/Explosive Surge.
Take the 3 out of Focused Impact (high impact bolt ignoring armor) and redistribute to Neural Overload (reduces movement speed on ion cell proc) and 2/2 Parallactic Combat Stims (generate ammo when stunned)