I was doing the quest [Among the Champions] from the Argent Tournament and another player was neaby hitting the NPC to disrupt my gameplay, preventing me at completing the quest. My combat log was empty so I asked the player in a polite way to stop doing that, and instead of apologizing and leaving me alone he responded me in a mocking way. He did not deny disrupting my gameplay and this is important, because I figured it could be used against him in a report.
I took a lot of screenshots to the whole dialogue (he not denying including), from the player hovering over my zone, lurking behind a building in preparation for his attack, of him targetting the Faction Champion I needed to fight, etc.
I presented all and the GMs told me "there is not enough evidence" and that "game disruption is for example when the NPC of the Argent Tournament are hit and reseted" (EXACTLY what I was reporting).
I asked the GMs how the entire dialogue is not proof and why don't they ask the player about my accusation. It would have been very hard for this player to explain a dialogue in which he is accused of disrupting gameplay and he not denying it or finding it weird. The GMs never answered my question.
When I asked what must I do the next time this player disrupts my gameplay I was warned of misusing the ticket system. So maybe here - at the forums - is the place to ask the GMs about the server they run and their procedures.
I re ask my question here: What must I do the next time this toxic player harrasses me or disrupts my gameplay and I want you to ban him?
Record a video I guess. A player saying in chat "I did x" is not proof that he did x.
I'll add that going by OP's words, he didn't take screenshot of the player resetting the NPC. Which, I assume, is pretty much the reason GM didn't intervene. No hard evidence = no action taken.