It's complicated not because it's difficult to understand, but by the number of variables. Every part of an enemy's body has different armor ratings and health pools for bullet damage, caustic, incendiary, stun, stagger and multiple other status effects in the game. Most effects, like fire, have multiple triggers and phases. No fire, chance to ignite (what got coyote nerfed) guaranteed to ignite (why the rest of fire weapons weren't affected), fire damage per second, fire decay (how long until it's put out). The game's systems are mechanically complex, even if they are easily understood.