You hit the nail on the head.. Slushes over sensitive pool hopping algorithm it taking its toll on slow miners "and even some big ones" .. I've tested it and compared it to other pools and have to admit it IS in my opinion WAY over sensitive... For this reason I think it tends to drive away more than just pool hoppers.. I really noticed it when my stratum proxy would flake out every now and then .. That's one of the things that prompted me to test with other pools..
If you have any moderate amount of hashing speed, then the exponential algorithm doesn't play that large a factor. . if the hashing speed isn't able to make a difference that offsets the normal number of shares that you would hash - then it will make a difference. I don't pool hop, but my payouts the last 20 rounds are all within about 8% of each other.