It's about how you play your deck, more than the deck itself. Strategy is key. You could certainly devise an awesome strategy with so called "weaker" cards if they complement one another, and the strategy is good enough.
I agree with Bryce. This game model is designed as such that UR and SR cards are so much more robust and versatile than R and N cards. Yes strategy does help, but it only gets you so far if your opponent repeatedly churns up card after card of URs
3 of each of those cards? that's a dead deck. A good deck is 20 cards. You wouldn't put 3 kuribohs/shard of greed/mirror wall all in one deck. that's almost half a deck. doesn't leave you much to make the rest of it with. Mirror wall..2 at most. Windstorm is just as great
Actually, it's not to far-fetched. I ran into someone with a 22 card deck that started out with 3 Shard of Greed and a Cocoon of Evolution. Took me a turn to get rid of Cocoon and they drew 6 cards. 2 Mirror Wall (a third one later game) and a Sphere Kuriboh (which the game decided for my opponent to keep drawing afterwards.) he played Jerry Beans with gravity axe and a trap jammer.