So took the time and reworked the robe based on the doppelganger concept and this is the end product:
Name: Fractured Soul
Description: Your target's soul splits into a vision of itself that is bent to your will and command. This vision will immediately attack your target and remain in existence for 1 minute. The power and strength of this vision matches your target and is exponentially increased depending on your pet bonuses.
What it really does:
When you activate the robe it copies your targets information and makes a temporary pet that will immediately engage the target. The stats of the doppelganger is 100% the same as the original target with the follow exceptions:
Size - 50% reduction. Some bosses are quite large, so this helps with the clutter
Runspeed - 150%. Some bosses are slow, some are fast. This is an average speed.
Damage - Base of the NPC * All applicable focus effects and pet powers.*
Target Type - Untargetable. This makes it impossible to buff the pet beyond the powers given to it. Additionally, helps with targeting issues.
*Note on Damage* - AA bonuses will not affect the doppelganger , however worn focuses, the enchanters current spell buffs and worn/worn2 bonuses will. Additionally while getting the normal % power boost from focuses, the pets will receive additional exponential bonuses depending on how strong the focus effect is. An example of this is the Talriem Event in Vex Thal where the end boss hits for 11,914 max. When this doppelganger effect is used on him, the doppelganger hits for 81,015 (with Dark Minion focus) and 95,312 (with Immortal Minion Focus).
A better example of the damage scaling -- In 1 minute Vision of The Sleeper vs. The Sleeper:
With Dark Minion Focus - Sleeper @ 71%
With Immortal Minion Focus - Sleeper @ 63%
Essentially, this just made the Enchanter donor robe absolutely crazy DPS for the 1 minute duration. The recast on the robe was also changed to 6 minutes due to the fact that the doppleganger is pretty much unstoppable (by normal attacks).