Apparently the new policy on raid stealing is to report early and in detail. Blizzard poster Belfaire, in a thread entitled 'Raid Harassment' explains in response to a post about a couple of people using a gullible guildmate's trust to snag his raid ID by 'asking for help on quests' and then wiping them repeatedly on Illidan attempts. Seems that now, if this kind of thing happens to you, (I once zoned into MC to find that, instead of half done, it had been cleared up to Ragnaros by another guild that had just accepted one of our mages as a member... he brought our raid ID with him, so they decided to take advantage of not having to do the first three bosses.)
The change in policy may not make much of an actual difference in some situations... if someone's wiping your raid on boss attempts, the GM's probably won't be able to act before your raid is done for the night... but it's miles ahead of the 'there's nothing we can do' policy that's been enacted in the past. After all, it is possible for GM's to teleport jerks off of the Isle of Quel'Danas when they're making the badge vendor impossible to reach, so maybe they'll start porting griefers like the ones in Ironhide's post. I can only agree with poster Podric, and Belfaire himself, when they say that it's about time for this change.