That’s not specific at all. What are they doing exactly? Unless they’re doing something that bypasses the intended functionality of the game content, then it’s not actionable.
Blacklisting battlegrounds was removed, see https://eu.forums.blizzard.com/en/wow/t/bring-back-blacklisting/127296 . You could absolutely go at another time, however that does not dissuade from the fact that they are blatantly bypassing an artificial timer in the game to repeatedly kill people. Once they get ahold of the map, they sit a group at spawn to kill you when you zone in and then keep the rest of the siege vehicles at the waterside graveyard and bombard it with siege weapons. Anyone that survives the salvo (siege weapons have no limit to targets they can hit) is hunted down (most players die in two salvos - combined with mass snares and you can’t live long enough to do any damage to the vehicles). Since half the team is sitting in ghost mode (goaded on by their streamers in the opposite faction’s chat) those 10-15 that cycle in and try are quickly beaten into submission, and can’t die fast enough to counter the resource gain from the Quarry and Refinery.
I did go merc mode last night and helped lead an Ashran to victory for alliance, but it is just as jarring playing Alliance (I have no interest in this) as it is inconvenient for these people to do Wargames (because they want to endlessly farm Horde, not each other). An amicable solutions to both parties is removal of the resource generation or a time limit - personally I feel the resource generation removal would allow them to farm to their content without clogging the Epic BG queue for hours (you can burn over an hour waiting for the queue [avg of 15 mins] to find out you got in this group, afk out and wait 15 more minutes for deserter to drop only to re-enter the same battleground due to the cycle of that 10-15 players afking out over and over).
Also, your reasoning was sound so I removed any hopefully tell tale information, however at this point it is well known who is doing it I’m afraid.
I am going to have to ask you to remove this, as the quote assists in identifying them and the subject matter it was relevant to was removed
So report it as an exploit using the in-game Bug Report option.
Don’t give directions for how to do the exploit in the WoW forums.
If you would like to report information regarding cheats or hacks to Blizzard, send it to email@example.com. Do not post it to the forums.