Arguing that a donation Katar should be one-handed because donation Bows were made one-handed is not a valid argument.
Damage can still be reduced and certainly the Sniper class can still be killed. Not to mention their damage can be completely nulled by pneuma, and it will be very hard to push their enemy out of it if they are wearing RSX, and even then it's a matter of changing to Immaterial arrows and launching a well aimed Skid Trap.
No, SinX does not a Katar which enables them to retain 55% Demi-Human reductions. Their evasion skills cannot compare and their offensive skills can CERTAINLY not compare. While it is true that Sniper's deal nice damage with Focus Arrow Strike and Double Strife, if ganged or against a formidable enemy, they'll still have a hard time killing them, and avoiding being targeted by multiple people at once. The Assassin Cross can easily backslide to avoid conflict until they have the opportunity to get an enemy by themselves, and apply Sonic Blow to them, which is spammable and HURTS. Though I think Sonic Blow damage needs a boost when not being linked, as it can be reduced greatly, enabling them to wear a shield is unnecessary due to it's already high versatility in PvP of being able to avoid fights they can't win and waiting to be an opportunist.
I say improve damage by a small amount and add a demi-human reduction to about half or less of what a shield with Usakoring+Forsaken Shield provides (20-25%). Maybe add an additional 25% reduction to magic damage since that would still be a big threat, but no more and less reductions could certainly be acceptable, but I say at least 15% reduction from all Demi-Human damage would be acceptable.