In my humble opinion, Rage may be the best part of zOMG! gameplay - it rewards you for doing what you're supposed to do (fight enemies), and encourages players to use abilities that grow increasingly splashy and attractive as combat goes on, making fights more fun and dramatic. In the past I've mused over completely removing the Stamina system and making gameplay purely Rage-oriented, but that would require quite a number of peripheral changes, as well. Regardless, congratulations for picking out what may well be one of the best features of the game. 3nodding
I think you hit a good chord with making your Rage-booster mirror Divinity - not only does that draw on the Stamina/Rage mirror, but Rage being 'profane' makes even more sense than Stamina being 'divine', which further justifies that mirroring. And given that you have an animation concept as well as a unique mechanical identity - and that you made an effort to point out potential flaws in your own ideas - this is one of the better-constructed ideas I've seen in quite some time. I'll admit I'm pleasantly surprised. sweatdrop
The issues I have with the suggestion are a little more fundamental to the gameplay than the scope of this suggestion; but assuming those issues were dealt with I'd be happy to see a ring like this come into being. The first of those issues is that I have trouble justifying new rings of any sort; of the 43-or-so rings we have, relatively few of them see widespread use, and many of those are used as fillers, rather than actually possessing unique roles. Until the devs can create an interesting balance among the rings we currently have, adding more to the pool doesn't seem like an ideal solution.
The second issue resolves to the nature of Rage; as I mentioned before, one of its strengths is in generating dramatic, incremental gameplay. However, because of the commonality of RR4 use, that impressive, dramatic impact is essentially watered-down - the issue, in my opinion, is that Rage is actually too easy to come by. I'd personally like to see the basic Rage function modified to diminish Rage gains as your Rage increases, making higher Rage Ranks much more difficult to achieve, compared to lower ones; I think this would also increase the use of RR2 and RR3, as their comparative ease to RR4 would make them even more attractive. It would likely follow that higher Rage Rank effects would need to be scaled up in power, but again that simply increases its dramatic impact.
All-in-all, the idea is absolutely clever and definitely usable; I simply wouldn't consider it the top of the priority list. Once some of the other issues are addressed, though, I wouldn't be at-all displeased to see your idea implemented... 3nodding