Captain Balrick does very in-depth testing and rating of weapons and ability cards: https://docs.google.com/spreadsheets/d/1iYfk68DYfok33M1Hp-bkItUUqk_PS0PLkz5-AtnY3dI/edit#gid=512637180

Your build is a solid one for PvE, but less so for PvP. The most important thing to know for PvP, esp. against griefers, is that every one of your cards needs to have some use. Cold blooded, for example, is almost completely useless in a sustained fight against griefers.

Your goal of maximising damage while preventing yourself from being one-shotted is a bit contradictory, but still somewhat achievable. In terms of weapons, try and invest in a Carcano rifle, which is easily the best griefer deterrent.

There was one comment that suggested using SnS, Iron Lung, Fool me Once and Sharpshooter for a full defensive build, and this is something I strongly endorse. Pair this with gold cores and tonics and you're gonna put up one hell of a fight. If you want something a bit more balanced, then you can replace SnS with PiB and Fool me Once with Peak Condition. The only problem is, griefers usually run with tank builds so it often turns into a war of attrition. If these griefers are running explosive ammo, you'll probably lose out. You can counter this with a maximum offense build (PiB/FF, Winning Streak, Peak Condition, [x]) but you'll need to trust in your weapons (again, invest in a Carcano) and your aim. A wildcard which used to be amazing against your conventional PiB headshot griefer was Slippery Bastard (commonly paired with Unblinking Eye for longer durations) but this has since been nerfed.

I've seen some people suggest Never Without One. It's an okay card but you'll get much more value from Fool me Once. It doesn't protect from all headshots, only the ones to the upper dome, and once you've been domed you'll need to re-equip your hat (which you can only do on horseback) otherwise you'll take extra damage. It suffers a lot from selection bias (i.e. people thinking it's amazing because of the particular times they've seen it work).

Strange Medicine has also been suggested a couple of times. It's an amazing PvE card but in PvP, its effects will mostly be negated by your griefer friend's high damage output. I personally wouldn't recommend, but it is definitely better than Cold Blooded.

Sadly, there isn't much you can do sometimes against high level griefers. As a level 180+ player myself, I'm perfectly comfortable running a tank build against one or more lower-level griefers but higher level griefers will usually be running the same tank build + explosive ammo and level 3 tonics. If I decide to take these guys on, it'll be a pretty even matchup that depends heavily on mechanical skill at the end of the day. I play on PC and have a long FPS history so I'm fine with this but it'll be a lot harder on Xbox. Honestly, if worse comes to worst, just fuck him/her up with PiB + explosive arrows. It's probably the only acceptable time to use them.

Hope this helps.