Quick, agile, and with greater range than the swarmtroopers, blitzies will remain a part of LEGION resistance throughout the game. They'll almost always attacks in groups of three or moew, and later on will always attack as part of a larger force. There's no special tactic beyond headshots for taking them down, but then none is really needed. Their own special attack is telegraphed well beforehand and is easily evaded, as you'll learn in the prologue.