I think there's something about the ground mechanic that I'm just not getting.
I was doing a basic exploration mission against Rommies and I kept dying on the boss pack. After about five tries I just gave up.
After the third try, I left and spent every EC and DL I had on better gear for my BOffs and it didn't seem to help any.
I tried everything I could think of, CCs, kiting, using all my buff/def cooldowns, but I just kept getting overwhelmed by the Engineers and all their gadgets. Even when using BOff focus fire on my target, I couldn't seem to burn them down fast enough because the Medics would heal them. If I went after the medics first, the engineers would get up their gadgets and overwhelm me.
The CCs just don't seem to last long enough to be very useful. Which is strange because the ship CCs are excellent.
Flanking damage is king. Always make sure someone is able to land a flanking attack either on the mob's side or rear.
I have Threat Control skill maxed so I usually use myself to attract the boss's attention, lobbing shots as I madly dash from cover to cover, making sure to position myself in such a way that my officers can flank attack and cause additional damage.
If its a open field with little cover or when I'm facing the Borg, I will usually setup a killing zone with a pair of officers on each side with me on the far end farthest away from the mobs. I will use a single long range shot from my sniper rifle to draw the mobs into the middle of my killing zone. In this arrangement, I usually won't shoot much. If I do shoot, it is usually a carefully placed kill shot so I don't get aggro, or to intentionally grab aggro of a mob that is getting too close to my officers.