After reading this Escapist article about escort missions in videogames, I can't agree more with the author...
Escort missions with computer NPCs is just nonsense... almost every time it becomes a pain. It is not entertaining nor "fun" to become desperate just because the computer is in suicide or stupid mode (the two most common cases).
Recently, in The Witcher game, (playing at normal difficult level) I've had to give up one escort mission just because the stupid lady I was escorting home was aggroing all the monsters towards her, making impossible for me to "protect" her (of course she had quite small life, so few enemy attacks and pum! dead).
After more than 7 attempts (trying different tactics and paths), I had to just leave the girl die and fail that quest :(
Please, until we can get really smart AIs, forget about escorting missions!