Man, i wish Scary_ghost was here to do the math for us at which damage the Fleshies get decapped (but not killed) with one shot. I would like to know the 2 borders (barely taking the head off contra the head is off but the fleshie only has 1 health left)
Don't forget Scrakes though. The Xbow on HoE 6man needs 2 headshots for the Scrake, no? So the Scrake would deffo need to be 1-headshotted with the M99.
The M99 on 6man HoE should just barely take the head of from a Fleshie (still leaving alot of health on itl) and then one more bodyshot to kill it off.
Remember this for balancing: The M99 doesnt allow you to carry anything else but the Machete/Pipebomb (at 13 weight), it costs a ALOT, both the weapon and the ammo (at 4000 the weapon would cost 1200 even with 70% discount, just like the AA12, which is alot of money on HoE) , it only has 25 shots (SO DON'T YOU MISS THOSE SHOTS!) and you move quite slowly with it.
Consider all the Scrakes and FPs and not 100% headshot / hits and also the occasional Siren and Husk and the ammo is looking VERY scarce.
So it seems just fine to me.
Think of this too: If all 6 players went Sharpie with the M99, your team would be screwed with the lack of ammo for the small stuff. You can't just 9mm everything, as you would be overrun very very fast.