Empathic bond is definitely worth the trouble for mastery when running a large rainboaw deck with FFQ or graveyards. Yes, there will be times when your creatures kill the opp before charging you all the way back up, but sundials, eternity, etc can help to mitigate this. I frequently used sundials to delay my win a turn or two and get mastery. Uzra is right, however. Mastery is intended to be difficult.
One other idea is to carry miracles as one person suggested, or heals as well. When I used to run a life/air firefly queen deck for farming AI3 (don't ask me why I thought it was a good idea), I kept heals around to make sure I masteried every time.