The text of the power states:
'While raging, as a free action the barbarian may leave herself open to attack while preparing devastating counterattacks. Enemies gain a +4 bonus on attack and damage rolls against the barbarian until the beginning of her next turn, but every attack against the barbarian provokes an attack of opportunity from her, which is resolved prior to resolving each enemy attack.'
Are the number of AOO the Barb would get when being attacked limited by their normal number of AOO's? IF the Barb had an 8 Dex would they get no additional AOO? If they have an 18Dex do they get 4 more? If it really every attack provokes?
If surronded by 6 goblins would the Barb get an AOO against all 6 of them attacking?
If the Barb is fighting a lvl 7 warrior that get 2 attacks would each of those attacks provoke also?
I prefer to just combine CaGM with Dazing Assault. Sure, you won't do nearly as much damage. But that's because there's less attacks for you to counter. And why are there less attacks for you to counter? Oh, right...because you robbed them of their turns before they could even complete their first attacks! :D