This has happened twice so far, in two different dungeons: My crew and I enter a room with a raised, inaccessible (or not easily accessible) platform with archers or mages on it. My 3 pawns, an archer and 2 mages, simply stand in place or walk back and forth, getting hit repeatedly with arrows/fireballs and not shooting back.

All I can do in these instances as a fighter is try to dodge or block with my shield and hope the enemy AI screws up and walks off the ledge on its own. Meanwhile, my pawns and the person I was escorting have all been killed.

What am I supposed to do in cases like this?

And on a related note, is there a way to tell my pawns to heal each other? I keep getting into situations where my whole party is at 1/3 health and I'll be out of combat for an extended period of time, but neither of my mages (both of whom have healing items and healing spells) ever actually use them on each other. Not even the "Help!" command seems to get them to notice that we're all nearly dead until it's too late (i.e. we run into a bunch of bandits).

Use the table in the Pawn guild to adjust their behavior or go to the merchant in the first Guard camp to buy behavior potions. You can make your main pawn prioritize ranged enemies or heal allies. As for downloaded pawns, I think you have to take a closer look at their stats and see which ones have which behaviors.