How are so many people formulating opinions on this, at this point? There's nothing there! gonk
I think the idea of summoning a duplicate (or duplicates) of yourself is interesting, but I'd very much like to see what you expect it to do. Does it attack when you attack? Does it attack independent of you? Is it just a puppet to soak up damage? There are lots of technical possibilities for a "Summon Twin" Ring, but I'll give you one hint; no matter how good it is, a 30 second duration with a 10 minute Cooldown will prove unusable. When you propose a Ring with costs that high, try pushing the power of the effect down so that the costs are reasonable.
Personally, I think it'd be resonant for the Ring to simply cost half your current Health and Stamina; it reflects the division between the user and the 'clone' rather well, though it may certainly prove hard-to-balance (depending on its effect). Which is, I suppose, why I was curious what you were intending it to do. sweatdrop
If it's attacking with you, it would be self-limited by the high initial Stamina cost - the most Stamina you could start with is 50, which you would burn through pretty quickly (particularly if you're trying to make good use of your 'clone'). Presumably, the 'clone' would initiate attacks of the same type as yours, whenever you do, utilising your stats. You very well could have higher Rage Ranks increase the number of 'clones' generated; costing additional Stamina and Health to match the split (i.e. 66% to make two 'clones', 75% to make three 'clones', and 80% to make four 'clones'). Alternatively (and possibly technically safer; the potential for 3, 4, or 5 simultaneous attacks lagging or breaking the game is higher than from just 2), you could simply have the effectiveness of the 'clone' increase with Rage (dealing 30% of your damage at RR1, 50% at RR2, etc.), and maintain the same costs.
If it's just a damage puppet, the Health cost becomes more relevant than the Stamina cost - since it determines how much damage the 'clone' takes before it breaks. The Ring would pass your Aggro onto the clone, and higher Rage Ranks would produce "sturdier" (Persistent Armor-bearing) clones. While there's not a whole lot of use for it currently, the main benefit would be in allowing it to 'soak up' debuffs or Crowd Control effects (which it would be, in essence, immune to). Personally, this version has a lot more of that 'build around me' appeal that I (personally) enjoy, but it's also got a slightly narrower usage.
But, still, it's important to find out what you were imagining when you proposed the idea. I suppose we can wait for you to get back and elaborate... sweatdrop
EDIT: You updated in the midst of my post. That's what I get for being unbearably slow, eh? gonk