Another thought in the 'Impervious/Penetrating' debate...
So, the scanrio is: mook with a Damage 3 pistol loaded with Penetrating 3 rounds vs. Paragon with Impervious 12 Toughness 12...
When the Paragon is hit, Penetrating acts and requires a Resistance test vs 18 (15 standard + rank), The paragon succeeds on a roll of 6 (equal or greater is a success). That means that it's a roll of 1-5 that will cause a Bruise, leading to -1 Toughness on future Toughness rolls. That's a 25% chance of failure.
There are 10 turns in a minute. Regeneration 2 heals 2 levels of damage per minute, or 1 level of damage every 5 rounds. Assuming a 20% miss rate on the part of the mook (unlikely), this means that every 5 rounds, the Paragon will be hit 4 times, and 1 of those hit will cause a bruise. That's 2 buises per minute that will be soaked up by the Regeneration 2 power. So, for 2 points, the Paragon can overcome the advantage that is given by the 3 point investment in Penetrating.