I believe that MassiveCraft is currently considered a "Generalist" server, not an RP Server or a PvP Server. That means that Roleplay shouldn't take precedence over gameplay except in designated roleplay locations like Regalia.
When in PvP premiums do not keep items on death, ONLY armor. Weapons, potions, enderpearls, food, golden apples - they drop these. The reason they "don't care" is because they have literally PILES of that stuff sitting at their base ready to replace what they lost. How do they get these piles? By darkrooming, enchanting, farming, crafting, and basically spending a shitton of time preparing for battle.
Non-prems can battle too. If they don't want to go up against the 'big bad OP premiums' they can always go up against each other. There is no rule stating that players NEED to fight premiums. If you don't like it, don't fight them.
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I'd like to conclude this post by stating that Premium doesn't make people OP. I'm a premium and I can't even beat average PvPers unless I'm on my faction territory. As such, Premium = / = Victory. Premium just proves you value the perks enough to donate, and if people DON'T value those perks than they won't donate. So, if you want to shut down Massive, nerf the perks. If you want to continue playing on Massive, shut the h*ll up and adapt to the modern gameplay.