I don't think Hastings is a bad footballer. I personally would not have released him. I think he is a better footballer than Brooks.
But he is slow and his attacking output is really low. His best attributes are he moves the ball around the field and gets a lot of touches, and his long-kicking game is alright. His goal kicking is unreliable - they keep having Lachy Miller take shots.
And the slow thing is a big deal - once teams figure out they can pile on the halfback without much fear of a quick run, they will continue to turn the screws on the halves, knowing they won't get beaten on a run. It's the exact opposite of guys like Walker or Adam Reynolds, who are really small but they threaten with the ability to kick short or run, which Hastings does not.
My prediction is that Knights are gradually worn down by teams that don't fear their attack and who keep shutting the halves down.
Knights' biggest strength is their forwards and backs are actually pretty decent, pretty competitive. Definitely big and strong and they run some lines. When Hastings looks out, he will have players like Best, Gagai, Fitzgibbon and Frizell on offer, Dom Young is a huge physical presence, especially for kicks. Hymel Hunt / Marzhew also pretty decent wingers.