Rapid Slashers were always miserable parasites, but once the Darkspore mutated them, they became deadly monstrosities. No other Darkspore entity possesses greater speed. Their lightning motion renders them almost hypnotic, but such a spell is broken when they move in to attack. Generally, slashers simply move away after inflicting a wound, but they always return, instinctively grasping that a thousand cuts kills as surely as any beheading.
Rapid Slashers are very fast, they are difficult to hit when they start running away. They are very dangerous in groups, because it is very hard to focus on all of them at once.
To gain a little advantage against the slashersm, use a Tempest hero from afar and when they start closing in use attacks to slow them down like Sage's Strangling Briars or the Time Bubble varient ability. Use attacks that can stun the slashers before they can get away, or when surrounded by them use Wraith's Ghostform to increase your dodge rating.