Nothing you can do as a guild leader is going to "fix" a systemic problem.
People rolling on loot they shouldn't? DKP! Right? It will help. But it won't stop someone from dumping their last five weeks of hard work into the toilet for an item that won't do them much good.
Getting bad people in the guild? New recruiting policies! Right? Sure, it helps a lot. Suddenly you have less morons coming in and less annoying people. But, every so often, they still get in. He seemed like a perfectly normal person for six weeks, then ... drama bomb! You need dogs posted outside your guild to sniff out the terminators. If only it were possible.
No matter the problem, no matter the novel solution, you're never going to get things down to zero problems. You reach a point where the added policies and systems to finish off the last 10% of the issues take 90% more work. I'm sure most people stop at the 20/80 mark.