The Importance of Being Denethor

[Voralphion]

Very good topic, a few things though,

Denethor can still be compared to Saruman, who was, though a Maia, fully corrupted by Sauron’s will.

Denethor wasn't corrupted by Sauron's will as Saruman was. Denethor's madness was partly due to the general strain of using the stone, and partly due to dispair. Sauron was not able to break Denethor's mind, but was able to control what he saw. Sauron showed him his vast armies and this caused Denethor to lose hope and sink into depression. This along with the loss of Boromir caused him to go mad. Saruman on the other hand wasn't strong enough to resist Sauron and so had his mind overthrown. I believe this is mentioned in the Unfinished Tales section on the palantiri but without my book at the moment I am unable to provide direct quotes.