There are many good Cards around:
Deathrite Shaman,
Jace, the Mind Sculptor,
Liliana of the Veil. I also love
Stoneforge Mystic (okay I play Stoneblade^^) and any Chandra because she is my favorite Planeswalker that I made a phone case with her on the back.
For your Sorin Problem.
He is a vampire planeswalker and called
Sorin Markov. First mono black later black and white. Also he is called
Sorin, Lord of Innistrad and all his abilities are related to create vampire Tokens, buff creature, destruction and playing with life Points. Cards like
Anguished Unmaking are telling the plot about Sorin, Innistrad and Avacyn.
I think he is a cool character and planeswalker but now with kaladesh and aether revolt we won't see him since he is home in Innistrad and have less connection to the gatewatch and Jace. Back to the card itself. I'm not an expert for modern or commander but probably playable in commander ? 6 mana is so expensive. There is one Legacy deck which could play him in a green white black list and is called NicFit. The deck plays a unique style which ramps mana with
Veteran Explorer and plays around 5-6 Basics. turn 3 a
Sorin, Grim Nemesis is brutal for every Opponent and he provides you with card advantage which is always a problem in this deck. In a red version you see
Chandra, Flamecaller for a fast clock, card advantage and mass removal.
Sorin, Grim Nemesis is not the best planeswalker and doesn't see any play besides NicFit.