are you using 6 or 12 point sockets? try a 6, i always find they dont slip as much (i said i find - i dont want some physics person coming stating why it makes no difference!) hahaa
have you got an impact gun or anything like that?
Your absolutely right, a 6 point hex can apply much more torque without rounding the corners off. I never use 12 point sockets unless it's for a 12 point bi hex nut or bolt. Absolutely useless for rusted or seized bolts.