After some struggle over the weekend, I was finally able to integrate MT-D*-Lite into the game. And while the enemies are able to find their proper paths, due to the nature of algorithms and given the same environment, enemies will always pick the same path. This is expected behavior, but we needed the enemies to at the very least spread out and not line up in single file for easy picking. Thus, we begin additional research on grouping and swarming behaviors. We stumble upon another type of pathfinding method, Ant Colony Optimization, that is beneficial in a hive-like situation where you have multiple agents attempting to find the better path toward a common goal. This sounds perfect for our game, so I decided to implement it.
ACO works by sending its agents out to the environment in a random direction and have them discover and venture around the world until the agent has discover its goal or something beneficial; at which point, the agent will retrace its steps leading to the goal and leave behind a pheromone that attracts other agents to more likely to follow its path. Unfortunately, waiting for an enemy to free roam the world until it finds the goal is not the type of behavior we envisioned for our game. However, not all is lost in this research. The concept of leaving pheromones can be adapted to get the separating behavior that I was looking for. When an enemy travel over a tile, I would increase the weight of the tile to discourage our enemies to traverse to that tile.
Implementing this adoption of ACO was fairly simple. However, the integration with MT-D*-Lite has produced a challenge. Pheromones are left behind and dissipate over time. This results in a constantly changing weights of tiles. By itself, it is perfectly fine, but because MT-D*-Lite reevaluates its path every time it detects a cost change for traversal, this caused a major performance hit on our game. So much so, that I can only have about 5 enemies before the game is unplayable. Obviously, this is not ideal; therefore, I have reverted to using A* for the time being until we can solve this issue.