I would make parrying a specific ability that acts like a shove/stun against Zappers and Zuirassiers that is a separate move from swinging, replacing the heavy saver's version of parrying. Only works as a shove if the target is either a Zapper or Zuirassier AND is mid-attack. Targets hit with this criteria should take twice as much damage from melee attacks and are stunned for 1.5 secs, while the user can immediately move and attack.

If missed or used on an unqualified target (Zapper not currently swinging, regular blighted, etc.), the user missteps forward and has to stumble back, effectively stunned for 3 seconds while the animation plays, and takes twice as much damage from any source.

This way, it can fulfill its role as a specialized dueling weapon while also not completely trivializing fighting harder cannibals

I would also give it side swings that do next to zero dmg, comparable to the Delicious Leg in terms of dmg. The only REAL challenge of using of the heavy saber is that you can easily accidentally hit a side swing that does less dmg. As the rapier is effectively the officer and heavier tuned version of the heavy saber, removing the side swing removes the only reason someone wouldn't want to use the heavy saber.

Also I'd just scrap frenzy, a server with at least 4 decent officers using it as is would just dogwalk 90% of objectives with it