The others aren't bad? Are they? I mean they're not great or anything......
They are certainly not terrible. Hellfire Trap is efficient Damage, Teleport Trap can be very useful positionally, and Spiked Pit Trap can anchor someone where you want just long enough to really hurt them. I have had all of them in books (probably still do) but not many.
All of them require some work to get them working, as well as predicting where someone will move, and persuading them to do so (much easier now we are seeing more zone enchantments). Hellfire Trap is probably best used to protect a zone that is likely to be attacked, the other two have more uses, but need supporting more, but they can all be reasonable cards in the right book.
Hydrothermal Vent doesn't require much work or support, it's more efficient as a damage source, and you could throw it in pretty much any book and get reasonable use from it. It's got some weaker points too, but on balance it's much easier to get your money's worth from it.
