Firstly, it’s worth noting that as a new class, Demon Hunter received fifteen cards each expansion during the Year of the Dragon, as opposed to the other classes’ ten cards. This leaves them with more cards in each expansion from this year, and thus more cards to use in Standard as of next year.
Blizzard probably liked the four cards in question well enough in design and/or balance that they consider them to be viable “Core” cards for the year.
By using four of Demon Hunter’s presumably sixteen card slots like this, they do not have to find them elsewhere.
This is especially important because Demon Hunter does not have Wild cards to choose from like the other classes do.