Rescue Bounty/Incursion mission doesn't seem to work with stealth gameplay

[TGDM]

 

I've tried doing this a few ways: Sniping them at a distance, hushed sniping and making sure none of them get alerted between kills, and Equinox/Ivara sleep. Only the last one has worked with any measure of success. The webm above clearly shows a stealth takedown on each unit without alerting the others, but the timer started on the very first kill.

It's been like this since release and could use a bit of polish.