I'm working (very slowly) on a primer for this cube. Please bear with me as it slowly updates.

S-Tier Cards
Any given Powered Vintage Cube contains cards that are easily top-tier, the best of the best. I rate the following cards as S-tier. If one of these is in your pack, it should almost always be taken regardless of the other contents of that pack. Some of these, such as the mana rocks, are extremely useful for any given deck. Others, such as Time Walk, Ancestral Recall, and The One Ring are build-around cards that can shape the future of your draft. Here are some examples:

Some other notable S-tier cards are Mana Crypt and The One Ring.

A-Tier Cards
A-tier cards are among the strongest that would be found in most cubes. These are extremely powerful cards and should be the cards that you keep an eye out for early in the draft. An early A-tier pick will often help you determine your picks for the rest of the draft. However, they are also still very good on their own, and most are capable of winning games single-handedly. Here are some examples:

Some other notable A-tier cards are Seasoned Dungeoneer, Dark Confidant, and Otharri, Suns' Glory.

B-Tier Cards
B-tier cards are cards that have powerful effects on their own, yet get better when paired with certain other cards. Many B-tier cards are part of A+B combos or have limited functionality without a pair. While pairing with specific other cards maximizes their functionality and turns them into game-winning cards, B-tier cards are perfectly playable on their own. Here are some examples: