Recently, I’ve used petards often, but I can’t figure out if I should use them against my opponents’ castles, or town centers (that is, when they have more than one).
Also, should petard train time be decreased? It wouldn’t cause too much problems for civ winrate, since almost all petards are generic (exceptions being Aztecs, Gurjaras, Incas, and Portuguese) and have no direct bonuses.
In a ladder game I use Petards mostly against Stone Walls (e.g. on Arena). Sometimes they can be useful against Castles but in most cases it is better to save the food, go up to Imp and get Trebs/BBC out.
In Regicide or Sudden Death game modes they can be a lot more useful.
I think reducing their training time from 25 to something like 20 seconds could be a good change.
IMO, the best usage for Petards is if your Castle is being rammed and you don’t have access to a melee unique unit.
Petards are most useful for taking down a defensive structure quickly. They also have a niche use case where two enemy castles are very close to each other. Otherwise, other siege units are more cost-effective.
Basically, Petards are intended to get the job done before an opponent can react. So breaking through a wall in Arena without giving the opponent a chance to rewall. Or destroying a castle in seconds (which takes a good number of petards). Or instantly destroying a TC in sudden death. In most cases, you don’t need to destroy a fortification that quickly.