This is perhapse a bit late for the "party", but I have a few ideas for this as a weapon.

#1
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-10 hp
+33% damage on all primary weapons
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#2
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Reduces knockback by 50%
And gives the huntsman weapon a strong knockback
(The downside being that it takes up the valuable 2nd slot)
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#3
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Eliminates all fall damage.
Player is 10% weaker to all types of damage.
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Don't worry I don't think there ever was a party, and I don't think eliminating fall damage or increasing knockback would make much difference for a sniper since they are usually away from the action and if they are getting close enough to get knocked back they are likely to die pretty soon anyway. The secondary wep slot on the sniper isn't very valuable either because it is used for the razorback, the daggershield and the camper's what'sitsname. These all come with their fair share of deabilitating stats which tend to counteract the advantages of the item and be equal. The only really usefull secondary weapon is the jarate and that takes a while to reload so doesn't effect the game too often.

+30% damage on the sniper's sniper rifle would be quite usefull (I don't play sniper much but I think it takes two shots to take out demos and soldiers with body shots and three or four for a heavy. I don't know if this would result in less shots being needed to take full health for any classes since usually there is a decent amount of health left for theose classes which can survive. I hope I am correct about some of this, as I have said, I don't know much about playing sniper.

Would -10HP make too much difference to snipers? I am pretty sure that is a sniper's health is reduced to 10 then they will die quite soon, maybe if the sniper is fighting a spy but without a SMG the spy would have a great advantage unless the sniper was good at melee and on full health. There are few classes which a sniper has to (or can) deal with using the SMG and these are probably the spy and the scout (if the scout needs to reload and is low on health) the medic would be possible but would probably not be fighting directly with a sniper unless they were a noob who could be taken out easily with any wep. My point is that snipers do not tend to be in high speed fights unless they are "top tier" and trust themselves to take out powerfull classes within fireing range.

Sorry for being so critical, there are also good things about your answer, you recognize that boots should have effects which make sense (fall damage or knockback) and you stats are not too ridiculous. I accept that your stats are focussed around the huntsman for medium range which is good since the set is based on robin hood, it is just that some of your stats were not very relevant. I admit that knocking an enemy back with the huntsman would be usefull against pyros but in this situation being knocked back by damage would actually help you to get away from enemies so does not counteract this enough.

I spent too long on this.

Thank you for reading and have a nice day/night.

Just so you know (I may be a bit late to the party too) It seems like just the arrows in midair is a bit... underpowered. Maybe add in a small speed bonus? (If you dont have a Jarate for slow or a SMG, you'll need to run a bit faster)

Oh, and if you'll be jumping i liked the fall damage idea

You say that they will need to be away from the action, but then why would they need to shoot while jumping? (sorry for all the comments by the way had trouble editing them )

maybe increases the moving speed and has decreased faling damage

Sounds good. But maybe it increases move speed while aiming, and has +15% drawing speed

Secondary slot
+ 50 speed while readying bow
+ no afterdraw
+15 arrow speed
+20 speed on wearer