what constitutes a card draw?
It only counts as a draw if the effect or rule specifically says "draw." Otherwise, it's just an action that resembles drawing a card. Specifically, Maralen of the Mornsong will not prevent you from putting cards in your hand with Narset.

This is specified by rule 120.5:


  If an effect moves cards from a player's library to that player's hand without using the word "draw," the player has not drawn those cards. This makes a difference for abilities that trigger on drawing cards and effects that replace card draws, as well as if the player's library is empty.