Cyber-Stein wasn't high risk, it was consistent due to the multitude of searcher and draw cards, even with Stein at 1. So they have no choice but to ban it.
Cyber Stein was never a tiered deck, but still it got banned. Lightsworn milling 15 cards on turn 1 is broken even if it is not tiered. Too many cards in this game deserve to be in the banlist.
No, wrong. Lightsworn will never mill the wrong card. Milling 15 cards on your turn 1 basically give you everything you need. They can just stop all your attacks on turn 2 and beat you on turn 3. You will never see an unplayble Lightsworn turn 3 unless you have Necrovalley activated.