Disregarding the dozens of other buffs and changes heavy Swords need (as a whole and individually), at the very least they should be able to kill minors and weaker elite enemies in a single swing [with no damage bonuses active] at the highest difficulties.
Nearly every special weapon archetype now has this capability, and with the amount of risk involved in using a Sword (baring a couple specific loadouts), it doesn't make sense that in high level content, minors take 2 swings, while weaker majors/elites take 3.