There are at least five who just patrol by themselves, for me it was easier wait for them than to take out the pairs who seem impossible to separate.
  As suggested above, the (nonobvious to me) trick  was realizing that when their red shield goes up they WILL NOT MOVE so just back up and laugh at them, thow/cast, until the shield goes away.  I died several times before working this out, and it's a looong jog back from the graveyard.