I agree with most of this.
As a blue player (i enjoy just doing my own thing regardless of tiers, so i'm actually playing 4c ) who flubbed at Eternal Weekend, i realized it was a mistake playing 3 Misstep, 1 Pyro, and 1 Fluster main deck. It was a regular grind against blue decks and kind of a tossup who wins; you know, down to who gets restricted draw spells first and makes a couple key outplays. I performed pretty well against shops i believe (although i played 1 in the main event and 1 in a side event only) because i picked a little extra removal main and my SB was kind of stacked against shops/outcome. But my g1's were still nightmares.
I think my choices could have been better maindeck. There is more decks with islands than there are with Shop, but picking an overly effective card like Pyro just costs you against shop. Probably even Spell Snare was better than that.
Aside from making better selections, which would bring shops win rate down, i still think Shops is right on the edge of possibly being too powerful. It could stand yet another restriction i think. I don't believe Shop itself should be restricted, because there are still cards the deck plays that no other deck does. Unlike restricting Thorn (which i feel medium about), there are cards in Shop that can be restricted without hitting another deck. Ravager or Ballista, for example, would not hurt another deck. This way, we can keep shop decks. I am not sure if 1 Shop makes an archetype, especially not necessarily without an unrestriction.