Stisnera acts as SPECIALIZED artillary; We haven't run up against any zombies or skeletons yet; even the lowest-level undead is immune to Stisnera's Mind Thrust, and with all that armor and no armor feats, she can't hit the broad side of a barn (except on a critical - just as the zombies/skeletons likely can't hit her, except on a critical - but Stisnera doesn't carry other weapons...). Jacob would do much better against such critters, however, as long as they come in a single wave of no more than about 4-5 hit dice. After that, he's out of enhancement and healing spells.
Oh, and Narf - I think I've figured out what we have been missing in our travels:
Random Encounters on the way from one place to another.