Blaster is my main. I've gotten 10+ kills on maps multiple times with this weapon and it's basically built for narrow choke points and ambushing around corners. It's a one shot with a direct hit (110-125 damage), 2 shot with the explosion damage (55-63). Obviously horrible for painting the map so I focus on pushing the enemy team back as hard as possible so that the rest of the party can paint.
I think people have such a difficult time with this weapon because despite it's explosion radius, the explosion only happens mid-air. If the shot hits the environment before, the explosion isn't triggered, so it actually takes some twitch skills to quickly line up your shots when someone is in your face.