You might want to establish more of your faction underground. Make requirements for member status more strict to keep folks from infiltrating. Isolate the underground from the surface by means of one-way portals, as this will keep recruits from accidentally (or purposefully) opening doors for enemies. Build an underground farming area not sharing any chunks with the underground, so you can grant access without worry of raid tunnels into your faction. Perhaps look into adding more roleplay/hangout areas underground to keep members from feeling trapped during raids. Val'roth is entirely underground and utilizes these safeguards in addition to others. I believe we've only had around five raid-related deaths since the server reset, and all of which were because they were outside during the wrong time at the wrong place.
As I said, I'm offering a simple solution for those who didn't build that way and don't want to have so much work.
innit, its the same psychopaths that sabotage a servers launch, cant believe anyone could do that in a game
Use negative potion effects such as poison, weakness etc. PvPers tend to dislike these potions. Or cobble bomb someone, fill your inventory with cobble and have 1 slot for a poison potion, and essentially suicide into them. But yeah, building underground is the best defense.
I remember my base was mostly underground, worked great until the invaders pearled to the top of the tower. And then it basically became a bloodbath because the only entrance or exit that we had was the top of the tower. I basically trapped myself and my fac mates to die. Note to others if they plan on building underground, have escape entrances, everywhere.