Can someone explain how to set the damage check threshold on Dredgen Sere when soloing the dungeon

My understanding is that when you compel the shadows instead of killing them, you prevent the damage check from being more difficult, and you add two seconds to your damage phase. This makes me think that the best solo strat would be to compel all five of them, instead of killing them, so that the damage check is easy to meet (preventing the arc coils from frying you during or after dps), and the dps timer is as long as possible.

Is this correct? Is there any downside to keeping the damage check as easy as possible? Does the timer just end after you pass the damage check?