Building destroyer would make a lot more sense for the orcs. I just can't see any creature short of some giant mega-beast avoiding traps by smashing through them. Having an orc rush into a weapon trap should really only make it more effective. I removed that trapavoid tag first thing. Of course, winning with a hall of traps is silly and boring, so I have to self limit to a single line of cage traps near a chained up dog as an early warning system and a few stone-fall and weapon traps scattered around the fort for when the front lines are breached.. hopefully to keep civilian losses to 50% or so. That shouldn't happen if I don't let too many in through the bridge airlock system...of course... lever lag is fun.
My experience so far has been a great deal of fun. I was given a bit less than a year to set up before the orcs came, which was far more time than I needed to dig in. The orcs usually come after a trade caravan arrives though, which has destroyed my human and elf relations due to shut-in madness. I'm having trouble finding iron, so my military is suffering for it, requiring me to turn to fortified archery and avoid melee...although, I'm getting a ton of steel from invading orcs, so that will be turning around very soon. The orcs come in far greater numbers than I can handle with 25% draft-rate, so I'll have to militarize even more. I already had one bad experience when I saw about 10 orcs and decided to let them in to fight... and there were about 30 that actually got in. I had the dwarven caravan there at the time though, and their guard formed the front line of my defense, with my military staying back to provide cover fire. The caravan suffered 100% casualties, and my military struck down to less than half of its numbers. I suffered about 10% civlian losses as a few orcs managed to make it into the fort (why I thought a few scattered traps should be built from then on..) Sieges are keeping me shut in for most of the year now. The brief breaks I get are used for mass loot hauling and dispatching of team woodcutter. Eventually, I expect the orcs will field more elite bowman, which will end my archery mayham... by then, I plan to have my military equipped in their steel...or better yet, one of the new metals if I can find it.
The orcs have created a cruel feedback loop with imported wealth. They force caravans to drop their loot on my map and when I do manage to kill them, they drop their own loot to. This added loot greatly increases my wealth, which seems to be leading to bigger sieges, which create even more loot. My imported wealth is sitting about 5:1 to my normal wealth, but nothing a few artifacts won't fix.
I look forward to sneaky drow and more megabeasts. Its great actually having a challenge to pit military against. It makes the trial of having to deal with equipment juggling mean something. My only real gripe is that the trading aspect of the game is nearly removed by constant sieging. It feels cheap having all their loot dumped on me for free because the orcs smashed them. I might just have to keep the trade depot shut off until I find a way to defend them against such reckless orc hate... hrrm.. might not be much of a gripe if I can find a way to pull that off.