Eve Online - what is the mix of NPC damage types?

There is a list of damage types that tend to be used by different NPC factions on the EvE wiki. It also lists which damage types tend to be most effective against them.

NPC damage Types

The various factions and pirates across New Eden tend to inflict particular damage types over others. The following is a list of the damage types inflicted by different factions

Damage done by NPCs

• Angel Cartel: All types, although mostly kinetic and explosive.
• Amarr Navy: EM and thermal.
• Ammatar Navy: EM and thermal.
• Blood Raiders: EM and thermal.
• Caldari Navy: Kinetic and thermal.
• Centii: EM and thermal.
• Coreli: Kinetic and thermal.
• Corpii: EM and thermal.
• Domination: All types, mostly kinetic and explosive.
• Gallente Navy: Kinetic and thermal.
• Gist: All types, mostly kinetic and explosive.
• Guristas: Kinetic and thermal.
• Khanid: EM and thermal.
• Mercenary: All types.
• Mordu's Legion: Kinetic and thermal.
• Odamian: Kinetic and thermal.
• Pith: Kinetic and thermal.
• Rogue Drones: All types.
• Republic fleet: All types, mostly kinetic and explosive.
• Sansha: EM and thermal.
• Serpentis: Kinetic and thermal.

Best damage to do to NPCs

• Guristas - Kinetic
• Serpentis - Thermal or Kinetic
• Mordu's Legion - Thermal or Kinetic
• Blood Raiders - EM or Thermal
• Sansha - EM or Thermal
• Angel Cartel - Explosive
• Mercenary - Thermal

I've found the missions DB at eve-info to be the most helpful source for damage types. Some of the data is stale, but users often post updated info in the comments. Even with stale data, this is a very useful place to find out exactly which resistances you should use in a specific mission.

There have been a lot of changes in the game during its lifespan, but NPC damage hasn't ever changed. There have been new NPC combatants added to the game, but the existing ones are the same today as they were the day they were introduced.

Well, AFAIK anyway! 8 )