I'd say it's definitely "harsh" in the case of individuals who have never had the opportunity to hear Jesus Christ's gospel. I mean how can a person be expected to accept Jesus if he has never heard of Him?
It is true that the bible doesn't appear to go into clear detail on exactly how this is handled, but there are passages that refer to this idea.
Romans 2:12-16
12 For as many as have sinned without law will also perish without law, and as many as have sinned in the law will be judged by the law
13 For not the hearers of the law are just in the sight of God, but the doers of the law will be justified.
14 For when Gentiles, who do not have the law, by nature do the things in the law, these although not having the law, are a law to themselves
15 who show the work of the law written in their hearts, their conscience also bearing witness, and between themselves their thoughts accusing or else excusing them.
Jesus' words in Luke 12:47-48
47: "And that servant who knew his master's will, and did not prepare himself or do according to his will, shall be beaten with many stripes."
48: "But he who did not know, yet committed things deserving of stripes, shall be beaten with few. For everyone to whom much is given, from him much will be required, and to whom much has been committed, of him they will ask the more."
Seems to imply that punishment for those that have not heard the gospel is different.
Acts 17:31
"Because He has appointed a day on which He will judge the world in righteousness by the Man whom he has ordained. He has given assurance of this to all by raising Him from the dead."
This passage is translated as such in the King James version of the bible. Others say "fairly and righteously". As I do not speak the original language I can't offer you a direct translation of the original text. However, the general idea being that people are judged fairly and justly (As you implied in your post, it would be injust to live and die a brief life, never be really told much of anything, then be sent to hell for it).
I know it isn't cut and dry information detailing exactly what will happen to such people but nonetheless the Bible does touch on the idea that people will be judged according to appropriate criteria depending on their circumstance, even though it doesn't explain it fully.