At the point that I want to do raiding with my characters, I'll be in a guild and I won't have to worry about ninjas all that much. I mean, shit happens but name and shame with tons of screenshots from the guildmates will wreck a reputation.
Doing 5 man instance runs with non guildmates? State the loot rules in 2 sentences at the start, screenshot it with the Datestamp, and go for it. Everyone should be rolling Need on BoE blues or exceptional greens (like wands with +healing, etc) due to high market value. As for the other items, I'm not going to stress over it much until the level 60 stage, at which point I'm just going to do instance running with friends or guildmates.