I understand completely where you both are coming from. My point of view is, that the restricted/banned lists are in place to keep a balance in the game. Thus, individual cards that are broken are placed there. Most of these cards have extreemly dramatic effects that can produce a simple game winning situation.....(Time Walk for example).
I have never seen (although I am sure someone else has) a game soley decided by the card Sol Ring, or any combo using it. That is why I think it is not quite as dangerous a card as it seems to have been deemed. I do think it is powerful, but no more so than dark ritual, or other fast mana effects. Plus, it is pretty simpe to sideboard against it (although as a casual player, I never have sideboards).
This is just my opinion, and I submit to the decisions of those in R & D because they are being paid for a reason: Generally speaking, they are smarter/better than I am at this.