...Are you trolling?
3 turns would be an understandable, yet still overpowered, argument, but you went straight to FIVE and put SIX+ as an option.
You realise that with 6 shards, that last 5 turns, you'd have 30 turns of invulnerbility + 6 sundials. You can outdeck pretty much any deck in the game that doesn't have an eternity.