Share them! There are so many different ways to be effective- and I think some of the difficulty complaints could do with a pinch more strategerical thinking.
One of my favorites is having a rogue sneak behind a group of enemies before a fight (rest of party is out of sight), then use the invisible skill. The sound of the invisible spell will grab the attention of all the nearby enemies, but they won't be able to find the invisible rogue- then the rest of the party can advance into favorable positions while the enemies are distracted / looking in the direction that the rogue disappeared in.
The teleporter pyramids can be surprisingly useful in combat, too- especially if you manage to place one in an advantageous spot before the fight.
