Use skill just before battle and you get chance of double damage. Really good on power shot on crit hit. I've used the skill and then opened up with the normal combo - shot, power shot, shot - and had something like 188 + 188, 236 + 236, 188 damage for the opening 3 shots. Enemy died.
Im only lvl 13 by the way.
The skill is good, but the new skill points distribution sucks shit. Previously the ranger couldn't quest properly now he's quite good. But the Druid, bloody hell the druid rules the roost questing for FB now.
Well that's my opinion anyway.