The issue is not the Hive mission, it's Borg in general post s7. Damage of several abilities have been greatly increased, to the point where unbuffed, invisible, torpedos can one-shot you. As well, the plasma DoT has been incresed about the same amount.

Here is a seperate thread on this in the bug subforum:

http://sto-forum.perfectworld.com/sh...d.php?t=452951