Annoying... Any clue if that's how it's supposed to work or if it's actually a half-baked bug fix?
I'm pretty sure it's a half-baked bug fix. While this certainly makes the fight more interesting from a DPS and healing perspective, it entirely removes 3/4ths of the minefield from consideration by the puzzle solver. You *have* to use the left row, since solving anywhere else results in a wipe (well, I guess you *could* use the right row if you really wanted to, but that's as silly as it has ever been). It also means that getting a bad roll on mine positions results in an auto-wipe due to enrage. When we did it tonight, we had to defuse five mines and it felt like we were pretty tight on the enrage. Six mines on the left row would be death, even if there's a nearly-clear path just to the right.
For those attempting this, Overload is a frontal cone with a fairly wide radius (more than 180 degrees, but less than 270). So, you tank him with your back to the wall while everyone else LoS's the tank on the other side of the droid. Sucks, but doable.
For reference, here it is from the point of view of the solver: http://www.youtube.com/watch?v=peLqN6_tc_k
You'll notice that, about halfway through, our sentinel was just a hair out of position right as we pulled the probe and got blown out.
Oh, and we asked around in gen chat after we hit this "mechanic" to see if anyone else was having the same issue. A couple groups were doing hard mode and confirmed that it was *not* bugged there, so it seems this is just a nightmare mode issue.