I know they were used against elephants - it even says that in their discription. But how often have you seen AI factions with no elephant factions around have them in their armies? I've seen it enough times to finally make them so stupidly high in cost the AI ignores building them. I've also seen them target my elephants when I've played a faction that has them maybe twice. One of those times they tried to charge them through a line of Poeni - that did them no good. Then the elephants just went and stomped on everything. The other time they actually made it to my elephants and they routed - but not before doing the only thing I needed them to do, knock through a wall (hence why they got routed, the pigs were on the other side ready to burn). I'm not saying they aren't realistic or don't have their uses - just the AI has problems with some units moreso than others. This is one of them in my opinion. It waste the AI's unit slot in that army at the least, it also waste a cities production time, the factions treasury when they are produced and every turn until they are killed due to upkeep. The AI is better served with a base melee unit as it just can't grasp how to use incendiary pigs. If it could, that would be great.

Sending them against cohorts or peoni though isn't very effective.