Having watched world defense on my server for a while, I notice patterns on what zones get hit a lot, and which ones not to bother.
New Thalanaar: typically some horde farming cloth or doing a quest out there.
The Sea Reaver’s Run: a daily quest
Farmer Saldeans Farm: some asshole killing low level quest givers
Honor Hold: Horde mad about something
Hellfire Peninsula: Horde just outside of Honor hold killing quest givers
Darnassus: a lot of spam is a world raid, a little is someone you’ll probably never be able to locate.
Darkshire: Some higher level thinking he’s hot crap.
Halaa: Lazy PVErs trying to get the mount
Nijel’s Point: Low level horde who got lost
Astranaar, Lor’danel: Horde of varying levels messing with Alliance.
I actually fought a BM hunter in Astranaar the other day, he got me though. They hit hard and heal like crazy. I could have played better, though.