As mentioned in the introductory post to the Sun & Moon series, the box ratios are assumed to be 3.0 regular Pokmon-GX, 0.8 full art Pokmon, 1.6 full art Trainers/secret rares and 3.0 Prism Stars
It also makes it quite difficult for your opponent to dig for answers, as they lose life whenever they draw cards
This card does have a powerful effect, but don't be surprised if it drops down to a more reasonable price a few weeks after the set launches and the dust settles
The Deathmark is a five-mana flashable Chupacabra that is one mana more, +3/+1 in size, adds in the valuable flash, and then can also mill yourself or another of 3 cards
Being basic doesn't grant any abilities to a land that it didn't already have, and doesn't remove any card types, subtypes, or supertypes