If your creature isnt a human, then its more powerful than it seems (cards like Lost Legion and Ogre Errant are extra powerful, since they benefit from both knight synergies and nonhuman synergies)
If you were a regular player back in 2011, it may be time to go through your bulk boxes
However, if you leave up enough mana in the same turn to cast Memory, you can have all players, including that opponent you targeted with Commit, shuffle their library
The best predictor is EDH use, especially since these are all legendary and likely to be Commanders for decks
There are cards that do change base power and toughness
Most major set releases also come with Commander decks, and with so many sets a year, there are a lot of Commander decks being released constantly