Erestor is the kind of hero that completly changes the way you play the game. He essentially solves card draw all by himself, but at a steep cost: you can no longer save a card for later rounds. Perfect for explosive starts and to never run out of fuel, but restrictive in what you can do. Your deck will need to be built around him. Will of the West is appreciated against certain scenarios, and he naturally synergies with any deck based on playing lots of low cost cards: outlands, Forth, The Three Hunters!, (MotK) Faramir, you name it.
He is also a great fellowship player: by drawing so many cards so fast and not being bothered by redundancy, erestor is amazing at quickly finding important uniques: Glorfindel's Light of Valinor and Asfaloth, Gandalf's Staff, Wizard Pipe, Narya and Shadowfax, Elrond's Vilya, Nenya and Mirror of Galadriel, Boromir's Steward of Gondor, Gondorian Fire and Blood of Númenor, Saruman's Staff, Elladan or Grimbeorn the Old's Orcrist, Lembas for everyone, and the list goes on and on. He is basically Santa.
Great if you want to mix things up, move away from the traditional deck building style, and create interesting and fresh gameplay decisions every round
10/10 would discard my hand again