I never used Photonic DOFFs with that ability, though I do have the shockwave torp on my B'rel with my KDF sci. I love it so. I use it with a normal Transphasic torp. Nothing like watching the damage mostly ignore shields and push back everything in it's radius.
15 seconds? Some people replying here apparently don't even know the console. It could be reduced to 47 seconds at best.
No you could get it down with the right combos to 10s or 15s. Not sure if any lower. This bug has been around for over a year and a half, but the best pvp fleets never used it because it was so stupidly, ridiculously overpowered. It was just not told to the general public so that morons wouldn't exploit the hell out of it. It is OBVIOUS that it shouldn't be on a cooldown close/equal to the stun immunity timer. Imagine 5 ships firing a aoe pushback/stun every 3 seconds. Yeah, it was that bad.