I never had a problem with Gale getting focus fired. I mean he got attacked but not any more than my other characters.
Though I pretty much always had defensive spells up do maybe the AI responds to that.
Best guess is they target the character with the lowest AC (something they shouldn't know in the first place really, but we shouldn't be able to check theirs either so meh) and since gale is usually the one with the lowest AC unless you can stack defensive spells on him like he's the freaking Overlord, then they'll typically focus the heck out of him til he is murdered to death.
