You can also observe the environments that we have observed our enemies in. The Cabal have been seen in the open spaces of mars, relying on their armor for cover, rather than natural elements. You could get around them and gain an edge, especially with the strength of heavy weapons and supers. Hive have been seen in close quarters, tearing at guardians with claw and sword. AOE damage will definitely help in your endeavors. Fallen constantly dive behind cover, rallied by captains for swift strikes. Kill it, and coordination will cripple. Vex are placed in spaces narrow in nature, with a few pieces of cover scattered about, and there head-shot immunity will definitely throw off guardians. They can be assumed to have comprehensive strategy of both open and closed spaces. And above all, the AI has been boasted to learn from your own developed strategies. In long battles, enemies will eventually realize how you are going about a specific situation, and will do their best to counter your delicate plots of destruction.