As a GM who allows optimization of characters, I have a couple of players that have tendencies to min-max their sheets, and noticed that one in particular has no trouble at all getting a ranged attack or a defense to a cost of 1, allowing him to get 10HD for a measly 20 points... 40 points for 10HD in both offense and defense...
We're trying a new House Rule, HD have a maximum width of 2. This means that they're mostly just for automatic-success, and generally won't be bought at more than 2HD. Having multiple HD will work, in that losing an HD or 2 to penalties will still allow you to automatically succeed if you have 3+ or 4+ HD respectively, but less effective than just buying 1WD instead. Good for null powers, or powers that aren't resisted, and even for offensive/defensive powers, since gobbling even a couple of die is useful, and they still work in unison with WD and regular D.
Thoughts before implementation?
This rule will, of course, replace, not stack with, our previous rule that the height of your HD is equal to your Dice Pool (or lower, declared pre-rolling).