It really depends on which setup I was using and which map.
For example, when I was doing Valkyrie vs Reapers I ended up getting sync killed by Banshees too often because of how I was trying to play it initially (bunch of BE's and AF debuff).
When I was doing Rio Collectors one of two things would happen. Either I would get hit by a Praetorian laser that would instakill me early and I would rage-quit, or I kept getting devices on Wave 3 or 6 that were a pain to complete within the time due to the wave composition and the map layout, as well as device locations. So what would end up happening usually was I wouldn't get them all enabled in time, although I did have some where I was lasered at the device from 10 miles away and rage-quit.
When I decided to do the Juggernaut, I had issues with getting swarmed on a couple waves and wasting equipment. Plus in this particular set of runs I kept getting Devices and Targets, and I couldn't complete some of them on time because I didn't have enough missiles or Ops. Incidentally, on the successful run, I got Targets on Wave 3 and 10, but only had 1 rocket left for 10 and 0 Ops. I got it but ended up using four gels on that one wave along with my remaining 3 or 4 TC packs and still nearly didn't have enough time to kill the last 3 targets.
Then there are a lot of them I "fail" because I don't get to the LZ in time for extraction.
As an aside, the other day I was looking at the objective data for my completed ones, at least since I started keeping a record of the objectives. I figured devices would have been the least common in my successful runs, but it turns out actually Packages had come up the least. Escort had come up the most. Targets and Hack were identical, and Devices were only slightly less common than those.