Slinger should just be a thin flat metal disc, it's purpose is to deflect most of the oil away from the actual seal. That's the basic design of it.
I only replaced a 4.6L seal one time about 10 years ago on a Crown Vic; at 230K miles it also needed a crank sleeve which fixed the leak. By the way, no seal will stop leaking after a while (unless maybe a rope type seal). If it leaks after installation it will only get worst. Did you replace the gasket for the seal retainer?
2002 Mustang GT, 2012 F150 SC EcoBoost, 2012 HD FXDWG, 2011 Nissan Juke (wife's)