These cards are better in mono white, red or blue because these colors can really use the mana ramp
Generally, when draw power and energy acceleration become more powerful and common, cards which require delivering high value for a high cost become more powerful
Once the rule officially updates with the release of Amonkhet , the converted mana cost of split cards will be computed as follows: When the card is on the stack, the converted mana cost will be the converted mana cost of the half that was cast
On one hand, your opponent might be playing them as well, making them a liability at worse, and a game of chicken at best
So, instead of painstakingly finding the probabilities for each hand arrangement, you can find the probability of drawing the target card in 6 random cards (for the example with 2 copies, the probabilities are dhyper(0,2,58,6), dhyper(1,2,58,6), and dhyper(2,2,58,6) for 0, 1, and 2 prized respectively)
On the other side are the players, who see the Reserved List as a massive barrier to entry