if they actually moved at their proper speed no jedi or sith would be able to block it except for the occasional stray bolt. Force foresight could tell them where the bolts were going to travel, but the human body can only move so fast, and human or alien no living thing can move at the speed of light.
blaster bolts are not lasers. they're projected superheated ionized plasma (kind of like lightsaber blades). since they're made of matter (plasma is kind of like gas), they are not traveling nearly as fast as the speed of light. blasters work like gaussian rifles in that they use electromagnets to propel the projectile, except in blasters the projectile is superheated gas rather than a caseless metal slug. therefore, if you had serious arm chops and were force sensitive, it would not be impossible to block blaster bolts with reasonable reliability.