@ tangor - last thing I want to do is change the filenames as these pages are old with tons of backlinks.
Which begs the question, do the pages getting hammered have common backlinks? Not every link is valuable. (Been there, done that.) Not offered as argument for argument's sake, just suggesting (as I discovered way back when dealing with the same thing) that those pages I mentioned had common back links which were not found elsewhere on my site. Things returned to normal and new backlinks eventually replaced those others... Meanwhile those backlinks highly desired and I knew to be good I sent a little email letting them know the filename had changed. YMMV, but sometimes one just puts out the fire then rebuilds the house.