Here's a breakdown of why these four buildings belong in B-tier: Goblin Drill, Mortar, and X-Bow are C-tier buildings. They perform below average in the December meta due to their rather high costs.

place a Mortar down to target one of the lanes. Use Skeleton King on the other lane and send in the Miner to take out key defensive structures. The Evo Dart Goblin takes on a defensive role ...