Tbf the other annoyance I have with that is you have to do it anyway halfway through the pack since your DoT’s duration is shorter than Shadow Crash cd (oh look the same problem as Aff and Vile Taint). Yes, you can take all the nodes with Seer and the extender, but that build is mediocre unless you are doing like gigantic MDI pulls where uncapped Seer damage is good.
Void Torrent or the Mindbender cleave should just tick your non-DP DoTs up when they do damage so you don’t get pulls where the pack is at 20% health and your DoT’s drop with Shadow Crash on cooldown for 7 seconds. Refreshing on an enemy that will die in 6 seconds feels awful.