Technically Nunu is extremely strong when played correctly. The problem is..... not enough people picked him up more than one game to learn the right balance of items/strategy/working his Snowballs to actually GET to play him correctly.
Don't discount him. He's actually an extremely solid rework.
And Yorick being crap? What world do you live in? He can split push better than any champion in the game. Can int push a lane better than Sion. He has a few counters, but most champs struggle laning versus him and most teams can't shut him down enough to stop objective creeping by either him or his team (when the other team goes to kill him)
Also, I've never seen Ryze actually enter Competitive play..... He's a Gold rated champ with an insanely high skill cap who is prone to gap closing, CC teams. Sure. He can hit like a truck when fed. I won't deny the chains are there, but there are so many counters to that chain that even good Ryzes generally follow the flow of the game's probabilities rather than "talent." Ryze wins based on his team, not himself. (It's kind of sad when a Low HP Karma can run Circles around a Ryze and destroy him)