The only excellent defensive typing there is is Steel. So no.
How does receiving double damage from the three top offensive types make it "excellent defensive typing"?
They're the top three offensive types because they hit Steel super effectively.
Beat me to it. Similarly, I doubt people would be constantly raving about Ice being a "Amazing offensive type," if it wasn't one of the few weaknesses of the ever-popular Dragon type.
More on topic, no, poison is not a good defensive type, because in comparison to Steel, nothing is a good defensive type. The only thing Poison has over Steel is a fighting resistance, and it's still weak to Earthquake, which every physical attacker and their mother carries. Plus, the majority of the types poison does resist are almost as bad offensively as Poison itself: Fairy has poor distribution, Grass as a type has near-perpetually been a laughingstock on offense and defense, bug has had it similarly rough, and Poison... Well, that gets redundant.