Dustin Hoffman here really tires hard not to give any sort of trademark Hoffman type of performance, he even curtails his particular vocal tics here. He portrays his character of a former professor and attempting to become a writer as a sort of an average man. Hoffman really stays this way through almost the entire film which is actually exactly the point of the film, and in this way Hoffman is effective. He stands in his spot in terms of the film just as David does as David is always viewed as an outsider by the locals, and as certainly imperfect by his wife who he does not pay enough attention to due to devoting himself to his work.
Hoffman is actually perfectly naive here as David, because he shows that David always stays as a fish out of water in the country, and never knows exactly how to deal with his wife's problems with him. Hoffman correctly stays in this average guy approach as he genuinely conveys that David does seem to be out of element when it comes to all that he must suddenly deal with that is completely different than his life back home in the United States. Hoffman interestingly always plays David with a certain degree of ambiguity though and in his portrayal of ambiguity there are certain shades to his character he suggests at.
Although Hoffman certainly does not portray David as anyone special he most certainly does not portray him as this great guy nor this horrible man either exactly but there are suggestions of both in his scenes with his wife. Hoffman always shows that David is sort of trying to affirm his wife of his love, yet Hoffman shows a certain standard quality to this like in a way David has become stale in showing his love to his wife. At the same time he consistently shuts her down as he wants her to fit his view of the relationship again it is not purposeful coldness Hoffman shows but rather an insensitivity to his wife's need. Hoffman's portrayal of this earlier makes his later inability to recognize that his wife has suffered a traumatic rape actually believable.
Hoffman's performance up until the end I won't say is fascinating but it most certainly fulfills its need, and brings to life the final segment of his character when David violently defends his home from the locals. A key aspect of the film and Hoffman's performance is that there is not really much of a transition of David to becoming a violent psychopath it is sudden as if it was always within David and just needs something to set him off. Hoffman actually due to his degree of ambiguity earlier actually does realize this sudden transition effectively, and his most powerful moments of his performance certainly come in the final act when the true nature of David is finally revealed.
In these final moments Hoffman is brutally intense as David, as we see that his violence is pure, and there is not a hint of hesitation. When he says he is going to slit someone's throat there is doubt there is no doubt in the truth of the words as portrayed by Hoffman, he is truly chilling because of the difference in David shown is so great. The important part of it is that seemingly pacifist David not only becomes a violent man but in fact a sadist. Hoffman is exceedingly off putting here because he shows that David in fact enjoys hurting and killing the men, because there was an inner psychopath in David all along. This is great final act turn by Hoffman. Although I won't say he is truly remarkable until this point, but his earlier moments frankly needed to be that way to make his final scenes are strong as they are.