The name of at least one face must be written on the substitute card, and any other information visible on either face of the card may also be written
The cost reduction can let you have an explosive turn, dropping all of your equipment or mana rocks into play
Make no mistake, these are far less powerful tutors than the greats, like Vampiric Tutor or Mystical Tutor, but you can get in the ballpark for the same casting cost as Grim Tutor
The pirate connection here probably comes from the informal names for these effects: looting (when you draw, then discard) and rummaging (when you discard then draw)
Paying four life seems a bit high for a single card, but the Library allowed you to effectively see into your future by a full two turns
Now, onto the decks themselves