Tempo Backlash

RoF just doesn't fit into what your deck is trying to accomplish. You could replace RoF for the time merchant. Running only 29 power is pretty light for this deck, giving you only a 68% chance of casting Worldbearer on curve. It also makes it difficult to hold up Backlash or Unseal. The time merchant will give you a little added ramp so you can hit your top end more consistently. If you're trying not to run merchants, you could try Obelisk to buff up your Raiders if you want a 4 drop, Polymorph or Xenan Initiation would give you another spell and form of removal. You could also consider Lunar Magus for life gain and a bit of card draw.

Also, Hailstorm with Teacher and Raider is pretty bad. You would be better served running more threats like Lunar Magus or Dawnwalker or possibly Polymorph for removal. Lunar Magus having 4 health makes for great anti-aggro. You could run primal merchant and keep a Hailstorm in the market.

Best of luck!