level 34 elec/eng blaster here...
end drain as a secondary is usless...
I can go up to a mob of +1s and drain all their end in 2 attacks if I use build up + ball lighting + SC (both slotted for pure end drain). +1 bosses, yup can do those too. AV....not on your life...
ps - i will be reslotting ball lighting to all damage again, it does little to no end drain even FULLY slotted for it..
pps - I love my fire blaster...