Reverse Holo printings and normal printings are treated as separate cards
There are plenty of amazing Un-cards to add to your Cube and these are some of the best
I imagine the price point alone might deter would-be Magic players who are trying to get into the game through this set
In counting card advantage, you would also say that Sign in Blood nets you one card, and any other consequences of casting the spell would need to be considered separately
The two target permanents don't have to share a type, which can result in some counters on permanents that would not occur normally, such as loyalty counters on creatures or +1/+1 counters on lands
Nevertheless, Dig Through Time, like Treasure Cruise, was extremely powerful in Standard, very pushy but overall a really positive contribution to the format that helped make Khans of Tarkir one of the best-designed sets the game has ever seen