Watching a large number of videos and noting down the hits or rare cards in general is a good way to figure out approximate rarities - mainly for categories of cards, but with enough data you can infer some information about individual card rarities, though it is not always easy to tell if the information is statistically relevant or not
Wall of Blood Wall of Blood has more utility as an enabler than a blocker
Vision Design got close, but there were some issues that Set Design had to work out
A good opening barrage can keep the opponent off-kilter, especially if it's a slow deck
I could go on for days about how so many of these cards brilliantly adapt characters, stories, and mechanics, but perhaps the most important part of the set is its art design
#5: Unsettled Mariner This two-drop Human (among other creature types) looks to add to the motley crew of disruptive Grizzly Bears that makes Humans so great