Its weird because they actually DO seem to have eyes or a face because shooting them in the face in real time always nets me far more damage. But damn they are extremely difficult. Even at level 20, if I get a rad scorp sneak up on me, I am gonna waste a few stim packs and if I have 2... well just look for a hill to jump off of.
Of course its better than being surprised by a deathclaw ^^.
I've found with my current skills...small guns is pretty high for level 6 and the radscorpions just shurg off the bullets. I would recommend trying explosives, since radscorpions have a melee-only attack, mines work excellent for me. Just through one in front of you and bait it to attack you. This works everytime for me. One or two mines later you have a dead radscorpion laying in front of you!
I just use the terrible shotguns and shoot them in the head in real time. 1/2 times it gets a critical hit and takes off 3-4 bars and I keep walking back so they never catch me. Also, now that my sneak is almost 100, I sneak up on them with ninja perk and shishkebab (with flame +50% perk) and with 1 sneak attack + 3 regular attack in VATS, they're pretty much dead.
"In the end, you're always on your own." - Squall Leonheart