The more useful the damage the harder it is to make the Trap I think. For example Holy damage can harm almost everything, Negative Energy has a nasty side effect so those two are harder to craft.
As for the traps power- I have seen traps taking doen the Hellfire Erynies in the abyss without the lass having a chance to react :P . Stack enough of them and it gets nasty, soon.
To boost your crafting skills there is a belt and some gloves in the game. Heroism, INT boosts, Prayer or friendly bards are of course useful as well.
Epic Traps
