I do enjoy the articles, as its neat to fool with mechanics and get issues everyone has an opinion on. I like the changes to the ogre mage, but now I feel the CR is too LOW!!
Here's my thinking:
A 5th level party has just gotten access to magics such as fly (hopefully, assuming there's a wizard in the party). But that hardly means they have it prepared or that they have it multiple times).
A creature that can fly at will cannot be followed by a 5th level party. Perhaps one guy can fly...maybe. And that means everyone else will be relying on ranged weapons. With fast healing and a better AC, the ogre mage can take a bit of punishment from ranged weapons.
In addition, with the SA, the orge mage can now do 5d6 +7 damage. That can easily take down a wizard in one shot. And again, 5th level is not so high that you would necessiarly expect a party to have see invisiblity ready to go. So ogre mage can come in invisible, strike down your mage, instantly become invisible again (swift invis) and be ready for more pain. And if the party manages to do some damage, he can fly out of range, heal up, and be ready to go again.
While CR 8 might be too high, I'm thinking CR 7 is a better number. Until you can reliably handle flying and invisible creatures, the ogre mage can be a true terror.