I just realized that the various hostile mobs of the Minecraft world all actually fit a pretty specific role that would be found in a real-world military.
- Zombies: they are the infantry units. They walk up to you and do close combat battle. Alone they are easy to take down but in groups they pose a challenge.
- Skeletons: these make for good artillery units. As archers they are ranged attackers however they also do well in close range battle. The only way you can really deal with them is get close up and hit them while strafing and striking between arrow launches.
- Spiders: special operations and assassins. Compared to the other mobs they are quite powerful. Their dark color means that in darkness the only thing that you can see are their eyes. Spiders are the fastest mobs which makes them hard to outrun. They are only one block high meaning that they can fit where the other hostile mobs cannot. They can also climb walls and jump pretty high. It's possible they will one day be able to shoot webs to slow down the player. They will climb on your roof and wait for you to come out. If there is a group of them, you can expect to be in lots of trouble.
- Creepers: suicide bombers. They are stealthy and more intelligent than the others. However I find their usefulness to be quite limited. Creepers are only good for one usage so it needs to be a lucky shot. Their utility is doubled when they are charged by lightning. In groups they will set up ambush formations.
- Ghasts: aerial assault units. A large group of them all firing at you can do some major pummeling and their ability to fly gives them the advantage of greater area coverage.
- Zombie Pigman: a better type of infantry. They have a mob mentality so they will all come at you at once, arguably making them more potent than zombies.
- Wolves: support forces. They are most effective when tamed as their HP and attack strength both increase. In a totally AI army of mobs they would be of no use unless you attack them first. However one or two of these as sidekicks of a user would be good.
- Spider Jockey: I almost want to dub these as cavalry. I find Spiders and Skeletons to be the two most dangerous mobs to meet up with in the Overworld and Notch decided to combine their powers. There are two main weaknesses: the jump of the spider is limited, and if the spider climbs a wall too close to the ceiling the skeleton will suffocate. Otherwise these are a powerful mob.
So if I assembled an army of mobs I would want zombies and zombie pigman squads in the front rows with skeletons supporting them. Spider jockies would be behind them and used for quick, deadly assaults. Spiders would be used to get at harder to reach or more valuable targets while Creeper groups would be delegated to ambushes. I would have Ghast squads raining down fire from the sky.
