3 point trait-restricted cards are what we often refer to internally as capstone cards. These are powerful cards that generally cost 3 points and are what reward you for playing more figures of a particular trait in a list. This card actually started off at 2 points and was originally just for Heavy Weapons with a placeholder art of a Clone Trooper holding a bazooka. Later we thought this unused art for Drokkatta would work better and realized we could also add Wookiees as a playable trait to the card to match the art, as Wookiees also needed a boost at the time and there were no Wookiee Hunters either. And then after a few seasons, we decided that even though Overwhelming Impact was not dominating the game, it made more sense to have a card that could in some scenarios add more damage than Assassinate also cost the same as Assassinate.
Overwhelming Impact is an offensive card designed to break through defensive bonuses, whose power scales to the defensive power of the defender. At it's base against a single defense die figure, it's +1 damage and +1 surge. But the more defense dice the defender is rolling, the more damage gets added, and the more defensive modifiers the defender is adding, the more abilities Overwhelming Impact negates.
Overwhelming Impact is now a great reward for players that play lots of Heavy Weapons or Wookiees together in the same list, and it's a great tool for breaking through defensive stacking and queen pieces.