At level 190 or so, even w/ lightning weakness, my max Blast would still only be about 71k... his neutral resistance really kills any chance of KB. You might get better numbers from appled CL.
Of course, if they bumped Blast to something reasonable like 750-800%, then it wouldn't be so bad.
Of course, if they bumped Blast to something reasonable like 750-800%, then it wouldn't be so bad.