I find Insurgency > Entropy > Quietus > Quietus works onders for double darkness as this kick starts the AM3 and deals significant dps.
Cross Reaper is also Distortion and does much better then Quietus at 1000TP.
Four step double dark
Insurgency -> Entropy -> Cross Reaper -> Quietus
Five step double dark
Cross Reaper -> Insurgency -> Entropy -> Cross Reaper -> Quietus
Four step light, Infernal is pretty powerful if you happen to have Maliase present.
Entropy (or Infernal) -> Guillotine -> Entropy (or Infernal) -> Insurgency
The problem with multi-steps is that each additional step shortens the timing window. This shortening isn't a big deal with 4 steps but 5 and 6 become difficult to do solo if your not a SAM who's over-TPing anyway. I'd suggest sticking with four step SC's, they give you a huge damage boost while being fairly easy to execute consistently.