Weird Wizardly Ways or Wizards are not Vulcans
Disclaimer – I do not own the rights to Harry Potter.
Scenario 1
Dumbledore has deliberately kept Harry ignorant of the world of magic, so as to avoid him becoming arrogant. Did he however think it through?
Harry has just learned that he is a wizard, and that he is expected to go to a school run by the person who left him on the Dursley's doorstop, and never came back to check on him. His re-introduction to the magical world, is carried out by a person who, though well-meaning, tells him that the wizard he is supposed to have killed is still alive, without explaining that Harry is still in danger from the man and his supporters.
Option A
Quirell meets Harry and invites him to come back the next day for a chat. The next day Quirellmort casts a diffindo curse on Harry's neck.
Option B
Harry finds out how to get back to Diagon Alley, and makes enquiries about alternative schools. A Death Eater hears, and gives him a portkey to "another school". Harry thanks him, uses it, and ends up in the middle of the Atlantic ocean.
Scenario 2
Dumbledore is concerned about the theft of the stone, and puts the stone in the castle at the same time that another target, Harry Potter is coming to school. He is aware that Quirrell is up to something but does nothing about it, except telling Snape to " keep an eye on him".
Quirrelmort tries twice to kill Harry, then decides that there are other ways to get back a body, apart from the stone, but he can get rid of Harry before he abandons Quirrell's body. In the middle of the class, he takes out his wand to demonstrate a curse, and reducto's Harry's head.
Scenario 3
Dumbledore sends Harry et al on a horcrux hunt, he however never tells them how to identify a horcrux, or what to do if it is hidden behind wards and curses, like the ring and the locket, the only two Dumbledore found before he died. What if one of the items they destroyed was not a horcrux, how would they have known?
Scenario 4
Dumbledore tells Snape (who is aware that the prophecy starts with "the one with the power to vanquish the Dark Lord...), that Harry must die. Snape never asks him, and when Harry is dead, who will kill Voldemort?
Scenario 5
Harry et al sees Snape dying, a man who they believe is a murderer, and who has never treated them well.
Option A
They cannot help him, he is not aware that they are there, they walk away, never finding out the secrets Dumbledore entrusted to him
Option B
Harry goes to Snape and gets and views the memories. He then remembers Slughorn was able to change memories and ignores what he saw.
Option C
Harry never asks himself the question, I am going to die, who will then kill Voldemort, instead he walks to his death, with the wand controlling the Elder Wand hidden on his person, does he leave it for someone else to use after he is dead, no, he keeps it for someone to find on his dead body.
Scenario 6
Twice before Voldemort has cast the killing curse at Harry, both times it failed. When Harry stands up before him in the forest, he does not try that curse again, he conjures a boulder and drops it on Harry. Voldemort's soul may be destroyed, but so is Harry's body. Worse, Harry's body remains a horcrux, but Harry is dead.
AN
I can continue, but by now you should agree with me, a number of actions were not logical by either Dumbledore, Quirrell, Voldemort, Snape or Harry. None of the illogical decisions by Dumbledore were done with ill intent, but they could have made things so much worse.