The gaskets we use on that pump are a black composition material; very
strong and solid. Haven't seen cork in a long time, and never a rubber
gasket.
I agree that any cork gasket there should be replaced with a new
composition gasket.
As far as ADs that aren't, there's another one that should be: the
horizontal stabilizer forward spar centre section cracks and could
fail. Cessna has a service bulletin on it, but sooner or later someone
will die because it wasn't mandated. Those who push down on their
stabs to turn the airplane are almost certainly going to have cracked
stab spars.
Dan