First off, rest assure that the back is alot easier to do than the front's.
Second, here's what I'd try (and this may be something you've already tried, or know), but it worked for me.
Now, assuming the car is up on jack stands, and you have a jack under the lower control arm, jack up the control pretty high so that you have lots of clearance. Instead of using pliers, take an alan wrench and stick down inside the hole in the top of the shock rod. See what I'm talking about? Then use an open ended wrench and yank that crap out of it while holding the alan wrench. The key is to make sure the rod isn't spinning at all (and it won't with the alan wrench in that top hole) while your twisting that nut off.
I've also found that by having the shock still bolted into the lower control arm on the bottom helps out a little too. Hopefully this helps a little.
Oh, and FYI, use some towels or gloves when holding the alan wrench and open ended wrench cause there will be alot of pressure and your poor little hands will hurt like no other. I'm sure you've already found that out by now though, lol! Hang in there man, your almost done.