X-Line as mentioned before has a much greater resistance to heat than pretty much any other brand of synthetic line out there. Only down side is that you can't get it with a safety thimble. Probably could get your own and splice it on there though. If you are reallllly worried about shredding the line up you could get the x-line pro for a pretty penny that has a 5 year no questions asked warranty.

http://www.offroadonly.com/products/.../x-line3.shtml

-Living Still

 

One of the cool features of synthetic line is the ability to splice it safely. I can't remember what the heck I had on my TJ, but there was about 15 feet of high-temp capable line close to the spool that was only marginally weaker than the main line. That piece was spliced like Chinese handcuffs (kid toy that you can't get your thumbs out of) to the other 75 feet. Both were rated well above the factory wire rope. The protector sleeve was just another piece of rope expanded to slide over the main line with heat shrink tubing on each end. First thing I'm doing with my new winch is ditching the wire for synthetic.

 

The only times I've had too power out under load were when I was lowering a disabled vehicle down something to steep for brakes and when my rig was the anchor vehicle for lowering rigs down a 'nose dive' where the probability was high they'd flip tail over nose.