Probably more of an exploit of a bug than a strategy but...

[cdsa142]

Turns out enemies in Journey to Perfection missions don't damage shields. I guess that's because the mission is supposed to end when you take a hit. I have a character that can basically keep a shield on forever, so I just walk straight through these missions, maybe stopping to use a low mana cost attack every once and a while.

[x4000]

Yikes!  Thanks for the note on that, that's definitely something I'm surprised none of us caught before now!