It has no direct benefit in battle, and using it will cost you your sole support skill slot so you can't use the other much more interesting and battle-useful support skills, but using this skill will allow you to get your job levels up, access the more advanced jobs, and learn high cost skills so much faster
It's probably a bunch of RTR bulk and the seller is trying to "get their money back." (there seems to be a common misconception among people selling their cards on Craigslist that their cards should be worth at least as much as the boosters they opened to get the cards)
Card draw doubling cards are not a common theme or strategy, but they provide players with a great way to gain card advantage
This allows phasing cards to keep counters, auras, and equipment attached to them when they phase back in
I really like signing cards
Granted, Price of Knowledge does cost seven mana, which prevents it from coming online as early as other options