Bear Stalker is probably the best anti sniping-weapon because you don't have to be as precise with it because it seems to have a larger hit box. If you are going to move around more use the bear-stalker, it has its drawbacks though (no pun intended), like it "misfires" a lot. As in you will draw the string back, release and it wont shoot anything. It has a massive headshot multiplier though, i think i have done 250+ headshot damage with just a tap of the trigger. Also you won't be able to rely on your secondary as much because if you get caught close range shooting an arrow it takes a while for your character to switch weapons because he has to reload the arrows first.
If you are going to be a bit more stationary use the buccaneer, i don't like it as much because the high power scope doesn't give you as much aim sensitivity so it can be difficult to hit fast or strafing players (the 4x zoom scope halves the damage so its useless) but you can drop people quick, especially if they get bunched up at chokepoints because unlike arrows in this game bullets travel through players. You will also have to rely on your secondary a bit more since your close-medium range abilities were nerfed.
If you do feel the need to use the marshal, I would use it as a secondary weapon on a close-medium range class to take out players or other snipers at a distance that you can't reach with your persuader or gatekeeper. The weapon has a quick raise and drop time so you should have little issues getting caught switching weapons, and if you aren't playing against players using hard target you can get some pretty crazy headshot killfeeds once you get good with it.
I have maxed out and gotten gold with all the sniping weapons and my opinion is that they are all useful, it just depends on your playstyle.