So I am bringing my concerns with BGC here as it hasn't been talked about much here and where it started is not the proper place for it. Firebug, you mention mana storms as an example of a BGC over 12, which I would agree with completely. The concern comes from places like the nazi death camps (auschwits is 16 in 5e), Hiroshima/Nagasaki (13), the five sacred mountains (one being lungs lair), the aura borealis, and the great cairn being over 12 for a BGC now, and other examples having doubled in BGC but not being over 12 (pyramids of egypt and stonehenge being 2 of them).
In previous editions (not just 4e so these didn't double for the extra dice we now throw, which would make sense for the scale as a whole increasing) these sites that are above the damage code start point were below the damage code start point, if only just. In 2e and 3e Auschwitz and Hiroshima/Nagasaki were rating 5 (1-10 scale where 6+ causes physical damage), in 4e it was rating 6 (1-12 where 7+ causes physical damage). So then what is the reason for Auschwitz and several other locations going from just barely under the deadly BGC but very difficult to work in, to higher than the damaging BGC as well as hard to work in