Terrain dice seem weak at first, but once upgraded they are super-powered. You need to know that placing a terrain dice on a previusly used spot adds to the counter, but does NOT increase the drop rate (i.e. 2x terrain dice on same spot is more than 2x as good).
With 2 gold terrain dice it's easy to get +10, +15 spots, which are so OP it breaks a lot of the game. With 3 ... you can easily cover the whole board in terrain +s. Much much more powerful than boost!