You will hear a similar story from Salford fans. He is by far the best player I have ever seen in a Salford shirt and has produced some breath taking individual moments that will live long in the memory. However it is sometimes easy when waxing lyrical about him to forget all the frustrating moments too, I am sure it was the same at Cas. In our recent games vs Wakefield and Leigh, he nearly cost us the game or at least our lead in those games by coming up with stupid plays that weren't needed and were unforced. It's part and parcel of his game though and when it comes off, it is pretty special.
I think you've seen since he left, a much more cohesive Castleford with a fantastic team spirit. Whilst Sneyd and Gale are arguably of a less standard to the quality of Rangi, both probably bought into the coaches philosophy much more than he ever did and play to instruction.
It will be a massive shame if he does leave, but it wont be the end of the world as some Salford fans will have you believe. I would even have a hefty wager that should we remain in Super League, a Rangi-less Salford Red Devils finishes higher than we did this season.