My strategy with meteor defense is usually to just pick one stack to protect and mostly to try to knock the meteors aside instead of killing them. If you can get a good shot on them from the left or right, they'll move out of the way enough to miss your crates.
The high terrain thing can happen. You might look to unlock double or triple jump enchants or Ride the Lightning, if that's still possible to unlock on the first continent... I don't know if that's changed now.