IT HAS BEGUN!
I COMPLETELY disagree with that assessment on Slasher. He has everything you need and does it very well. B1 is the best normal in the game and B12 is a fantastic stagger.I'm sorry to say that you've been missing out, my friend. Jason has been a high mid tier character since the big February patch. In particular, Unstoppable has been commonly regarded as potential low high tier material, since then. IMO, Slasher is still likely his weakest variation, overall, but it's comfortably mid tier and absolutely viable.