Mystic's Dark torment says the following "The mystic hurls a dagger that impales her target dealing damage over time. Nearby sand vipers focus on that target. If the target dies, a defense appears and attacks enemies."
1. Now after some testing i noticed sand vipers don't focus the dark tormented target no matter how close they are.
2. Sand vipers cannot crit after patch 17.0.
It works perfectly fine. I even got to place down all of the sandvipers in a public hub and I got them to all attack 1 dummy. I posted the image on my Steam account if you'd like to have a look.
I have noticed this as well. I was able to get the beams to focus 1-2 times on the Griblok Incursion, but have not been able to since. This was approx. two days ago and was with 3 turrents in one lane and 1 from a sepearte lane, so it may have been coincedence that all four targeted the boss.