I've mentioned that was one of my favorite features here before. I once blocked everything but the us for several days and redirected those people to google (to be fair that part was accidental lol)
I'm not familiar with all those plugins so I can't say definitively so its possible some of those are memory intensive, but nothing jumps out at me as a memory hog.
Just to be clear, are you using the latest versions of wordfence and wordpress?
tim