This is probably the most divisive legendary in Saviors of Uldum. Some players think it's going to be nuts, while others say it's completely useless due to a lack of lackeys (no pun intended) in Warlock class right now.
But there are two great arguments in favor of this card. The first one is that Blizzard will add more lackeys to the game in the future expansions, thus automatically increasing this card's value.
The second is the combo, which can be achieved with Glinda Crowskin. It gives all of your minions Echo, thus you can play as many copies of your 4/4 lackeys as you want.