What would you do in this case?

Its quite simple but more nuanced than it seems. I was a raid leader in Toc 25. DV drops and in the end 2 people had to reroll, both DKs. The winner of the reroll had StS and DBW HC trinkets, so clearly he doesn't need DV and I suspected he was rolling for a friend. Regardless of my suspicion, he claimed he was MS PvP which was never discussed, he simply joined as DPS and never said a thing all raid. I ultimately gave DV to the other DK since he was second highest roll and clearly needed it.

I havent been part of this Warmane ecosystem in 10+ years and I had no horse in this race, and immediately I got threats from the DKs with StS and DBW friends that I'm getting reported. On the other side, other people were threatening me with reports if I DID give the DK with "BiS" trinkets the item. Ultimately there was no winning since both sides were blowing up my whispers, I made a judgement call and gave the trinket to the lowbie DK that was second roll. What would you have done?

I think you did the right thing, but something to note- to protect yourself when you raid lead you should take screen shots of ms changes at the start of the raid. Chances are low this guy also documented anything if you do end up getting reported, so I don't suspect anything will be done- but in the future to protect yourself when you run pugs it is always a good idea to document everything you can regarding loot- especially highly valued gear.

So… how can someone get a BiS PvP item, which DV for a
DKs obviously is?