Ok so
@Perthmike did an excellent job in replying to your concerns and I agree with everything he said especially when defining to the limitations of Dothraki hordes.
I will say regardless of Dothraki fighting ability two key facts were known by Jon and all the other generals:
1) the only way to win the battle was to kill the NK
2) the NK would not be fighting in the front of the army or be near the zombies at all. This is based on every single previous encounter with the NK (frozen lake, hardhome, attack on bran and the original three eyed raven, fist of the first men, etc) which was known by first hand experience by someone Jon had been taking to (himself, Bran, and Sam)
Thus they must have known any frontal assault on the zombie army, like the one done by the Dothraki, wouldn’t achieve their only objective of killing the NK (the only way to win the battle) and was thus a waste of troops but still did it anyway.
By using the flanking approach I mentioned, they could hope to catch the NK either from behind the zombies (where he usually was) or if they saw a point where he was vulnerable like when he fell of his dragon and was alone without any zombies near him then try to attack him directly. Note - this would still be in the same nature of the Dothraki culture and fighting tactic.