Unfortunately, it lets the controller separate the piles, not the opponent, so the split often favors the Toymakers controller regardless of your decision
Oh, to be young and innocent
It's easy
It was so dominant that people even played Jace Beleren, the cheaper 3-mana Jace, partly as a weird answer to it, because the planeswalker legend rule at the time let you drop your own Jace and immediately get rid of your opponents
The expansion into many colors makes the deck quite a bit more expensive (in mana-cost and cash), especially on the side of the mana-base (the M10 lands may also be included), but I feel that the tradeoff where card quality is concerned can be descried as considerable
Deicide, Banishing Light and Temple of Plenty were all the deck needed to grow the beard