I honestly don't think 400 is feasible in T5 unless you lump in LB damage. Even on my best days when I'm hitting my stride, have all my cooldowns available at the right times, have battle voiced foes at the right times, etc... I'm still only maxing out around 340-350 at most. BiS, popping hq mega int, getting fester crits on Asceplius, Baning mega int + RS + Contagion'd DoTs onto everything in phase 1, etc.
The only time you can semi-reliably break 400 DPS is on AoE encounters, like turn 4.
