What he said, and this:
If you are accurate and coordinated with spotters, it's insanely effective.
If you're just popping off without a good team or platoon, it's a massive waste of time and credits.
Take the reload time to move around a bit, since counter-arty at that level can be devastating. You get a whole minute between shells, you can scoot quite a bit in that time. Just put the foot on the gas the second after the gun fires, though, in case they're watching your tracers. My method is shoot-pivot-haul ass for at least 50 meters, usually towards open ground (avoiding shrub-hunters) then look for a new spot, or just stay in the open if the screen kept the enemy scouts out. Find a new target or re-focus on the same one again, and repeat.