There is a paradox in Clash of Clans where the better your base is, the more resources you will lose. Here's how it works:

If my base is bad and the enemy gets 1-Star on me, I may have lost 198,000 gold but for the next 12 hours I'm safe. However, if my base is good they enemy may not get a Star, but I've lost 80,000, 100,000, 120,000, over and over again. Such losses can pile up to 500,000 over a 12-hour period. So I've gained trophies but lost the day's take from the mines.

Let's look at the existing system to see if we can fix this problem with a little modification:

50% damage: 12-hour shield
90% damage: 16-hour shield

Seems like there are a few numbers missing, right?

I'll leave it to the experts with playtester and game data to find exact numbers, but I propose 30% damage gets a 4-hour shield.

Actually, that's not really what I'm proposing. I'm trying to come up with a solution to the main problem: A well-designed base will lose more gold due to repeated pickpocketing, and therefore players have little incentive to design their bases well. (I trashed my TH7 design because it was winning too often, losing over 80k each time.)